Underground drilling device employing down-hole radar

ABSTRACT

Devices for sensing at an underground drilling device in communication with an above-ground locator involve transmitting a radar probe signal from the underground drilling device. A radar return signal is received at the underground drilling device. The radar return signal is processed at the underground drilling device to produce sensor data. The sensor data is transmitted in a form suitable for reception by the above-ground locator.

This is a divisional of Ser. No. 10/878,074, filed Jun. 28, 2004, whichis a continuation of Ser. No. 10/283,006, filed Oct. 29, 2002, now U.S.Pat. No. 6,755,263, which is a divisional of Ser. No. 09/955,675, filedSep. 19, 2001, now U.S. Pat. No. 6,470,976, which is a divisional ofSer. No. 09/405,889, filed Sep. 24, 1999, now U.S. Pat. No. 6,308,787,which are hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of undergroundboring and, more particularly, to underground sensing at a cutting toolusing down-hole radar.

Utility lines for water, electricity, gas, telephone and cabletelevision are often run underground for reasons of safety andaesthetics. In many situations, the underground utilities can be buriedin a trench which is then back-filled. Although useful in areas of newconstruction, the burial of utilities in a trench has certaindisadvantages. In areas supporting existing construction, a trench cancause serious disturbance to structures or roadways. Further, there is ahigh probability that digging a trench may damage previously buriedutilities, and that structures or roadways disturbed by digging thetrench are rarely restored to their original condition. Also, an opentrench poses a danger of injury to workers and passersby.

The general technique of boring a horizontal underground hole hasrecently been developed in order to overcome the disadvantages describedabove, as well as others unaddressed when employing conventionaltrenching techniques. In accordance with such a general horizontalboring technique, also known as microtunnelling, horizontal directionaldrilling (HDD) or trenchless underground boring, a boring system issituated on the ground surface and drills a hole into the ground at anoblique angle with respect to the ground surface. A drilling fluid istypically flowed through the drill string, over the boring tool, andback up the borehole in order to remove cuttings and dirt. After theboring tool reaches a desired depth, the tool is then directed along asubstantially horizontal path to create a horizontal borehole. After thedesired length of borehole has been obtained, the tool is then directedupwards to break through to the surface. A reamer is then attached tothe drill string which is pulled back through the borehole, thus reamingout the borehole to a larger diameter. It is common to attach a utilityline or other conduit to the reaming tool so that it is dragged throughthe borehole along with the reamer.

In order to provide for the location of a boring tool while underground,a conventional approach involves the incorporation of an active sondedisposed within the boring tool, typically in the form of a magneticfield generating apparatus that generates a magnetic field. A receiveris typically placed above the ground surface to detect the presence ofthe magnetic field emanating from the boring tool. The receiver istypically incorporated into a hand-held scanning apparatus, not unlike ametal detector, which is often referred to as a locator. The boring toolis typically advance by a single drill rod length after which boringactivity is temporarily halted. An operator then scans an area above theboring tool with the locator in an attempt to detect the magnetic fieldproduced by the active sonde situated within the boring tool. The boringoperation remains halted for a period of time during which the boringtool data is obtained and evaluated. The operator carrying the locatortypically provides the operator of the boring machine with verbalinstructions in order to maintain the boring tool on the intendedcourse.

It can be appreciated that present methods of detecting and controllingboring tool movement along a desired underground path is cumbersome,fraught with inaccuracies, and require repeated halting of boringoperations. Moreover, the inherent delay resulting from verbalcommunication of course change instructions between the operator of thelocator and the boring machine operator may compromise tunnelingaccuracies and safety of the tunneling effort. By way of example, it isoften difficult to detect the presence of buried objects and utilitiesbefore and during tunneling operations. In general, conventional boringsystems are unable to quickly respond to needed boring tool directionchanges and productivity adjustments, which are often needed when aburied obstruction is detected or changing soil conditions areencountered.

During conventional horizontal and vertical drilling system operations,the skilled operator is relied upon to interpret data gathered byvarious down-hole information sensors, modify appropriate controls inview of acquired down-hole data, and cooperate with other operatorstypically using verbal communication in order to accomplish a givendrilling task both safely and productively. In this regard, suchconventional drilling systems employ an “open-loop” control scheme bywhich the communication of information concerning the status of thedrill head and the conversion of such drill head status information todrilling machine control signals for effecting desired changes indrilling activities requires the presence and intervention of anoperator at several points within the control loop. Such dependency onhuman intervention within the control loop of a drilling systemgenerally decreases overall excavation productivity, increases the delaytime to effect necessary changes in drilling system activity in responseto acquired drilling machine and drill head sensor information, andincreases the risk of injury to operators and the likelihood of operatorerror.

There exists a need in the excavation industry for an apparatus andmethodology for controlling an underground boring tool and boringmachine with greater responsiveness and accuracy than is currentlyattainable given the present state of the technology. There exists afurther need for such an apparatus and methodology that may be employedin vertical and horizontal drilling applications. The present inventionfulfills these and other needs.

SUMMARY OF THE INVENTION

The present invention is directed to systems and methods for down-holesensing using radar. According to one embodiment, an undergrounddrilling device is implemented for use with an above-ground locator. Theunderground drilling device includes a cutting tool assembly comprisinga cutting tool and a sensor housing. A radar unit is provided in thesensor housing. A transmitter is also provided in the sensor housing. Aprocessor, provided in the sensor housing and communicatively coupled tothe radar unit and the transmitter, receives radar data from the radarunit and produces sensor data for transmission via the transmitter in aform suitable for reception by the above-ground locator.

According to another embodiment, a method of sensing at an undergrounddrilling device in communication with an above-ground locator involvestransmitting a radar probe signal from the underground drilling device.A radar return signal is received at the underground drilling device.The radar return signal is processed at the underground drilling deviceto produce sensor data. The sensor data is transmitted in a formsuitable for reception by the above-ground locator.

The above summary of the present invention is not intended to describeeach embodiment or every implementation of the present invention.Advantages and attainments, together with a more complete understandingof the invention, will become apparent and appreciated by referring tothe following detailed description and claims taken in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an underground boring apparatus in accordancewith an embodiment of the present invention;

FIG. 2 depicts a closed-loop control system comprising a first controlloop and an optional second control loop as defined between a boringmachine and a boring tool according to the principles of the presentinvention;

FIGS. 3A-3E depict various process steps associated with a number ofdifferent embodiments of a real-time closed-loop control system of thepresent invention;

FIG. 4 is a block diagram of various components of a boring system thatprovide for real-time control of a boring operation in accordance withan embodiment of the present invention;

FIG. 5 is a block diagram of a system for controlling operations of aboring machine and boring tool in real-time according to an embodimentof the present invention;

FIG. 6 is a block diagram depicting a bore plan software and databasefacility which is accessed by a controller for purposes of establishinga bore plan, storing and modifying the bore plan, and accessing the boreplan during a boring operation according to an embodiment of the presentinvention;

FIG. 7 is a block diagram of a machine controller which is coupled to acentral controller and a number of pumps/devices which cooperate tomodify boring machine operation in response to control signals receivedfrom a central controller according to an embodiment of the presentinvention;

FIG. 8 is a detailed block diagram of a control system for controllingthe rotation, displacement, and direction of an underground boring toolaccording to an embodiment of the present invention;

FIG. 9 depicts an embodiment of a boring tool which includes anadjustable steering plate which may take the form of a duckbill or anadjustable plate or other member extendable from the body of the boringtool;

FIG. 10 illustrates an embodiment of a boring tool which includes twofluid jets, each of which is controllable in terms of jet nozzle spraydirection, nozzle orifice size, fluid delivery pressure, and fluid flowrate/volume;

FIG. 11 is an illustration of a boring tool which includes twoadjustable cutting bits which may be adjusted in terms of displacementheight and/or angle relative to the boring tool housing surface forpurposes of enhancing boring tool productivity, steering or improvingthe wearout characteristics of the cutting bit in accordance with anembodiment of the present invention;

FIG. 12 illustrates a cutting bit of a boring tool which includes one ormore integral wear sensors situated at varying depths within the cuttingbit for sensing the wearout condition of the cutting bit according to anembodiment of the present invention;

FIG. 13 is a detailed block diagram of a control system for controllingthe delivery, composition, and viscosity of a fluid delivered to aboring tool during a drilling operation according to an embodiment ofthe present invention;

FIG. 14 is a more detailed depiction of a control system for controllingboring machine operations in accordance with an embodiment of thepresent invention;

FIG. 15A illustrates a boring system configuration which includes aportable remote unit for controlling boring machine activities from asite remote from the boring machine in accordance with an embodiment ofthe present invention;

FIG. 15B illustrates a boring system configuration which includes aportable remote unit for controlling boring machine activities from asite remote from the boring machine in accordance with anotherembodiment of the present invention;

FIG. 16 is a depiction of a portable remote unit for controlling boringmachine activities from a site remote from the boring machine inaccordance with an embodiment of the present invention;

FIG. 17 illustrates two modes of steering a boring tool in accordancewith an embodiment of the present invention;

FIG. 18 is a longitudinal cross-sectional view of portions of two drillstems that mechanically couple to establish a communication linktherebetween according to an embodiment of the present invention; and

FIG. 19 is a depiction of a locating/tracking unit that employs anapparatus for determining the location and orientation of a boring toolby employment of a radar-like probe and detection technique inaccordance with an embodiment of the present invention.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail hereinbelow. It is to beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the invention isintended to cover all modifications, equivalents, and alternativesfalling within the scope of the invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

In the following description of the illustrated embodiments, referencesare made to the accompanying drawings which form a part hereof, and inwhich is shown by way of illustration, various embodiments in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized, and structural and functional changes maybe made without departing from the scope of the present invention.

Referring now to the figures and, more particularly, to FIG. 1, there isillustrated an embodiment of an underground boring system whichincorporates a closed-loop system and methodology for controlling aboring machine and an underground boring tool in real-time. Real-timecontrol of a boring machine and boring tool progress during a drillingoperation provides for a number of advantages previously unrealizableusing conventional boring control system approaches. The location of theboring tool is monitored on a continuous basis and boring tool locationinformation is transmitted to a computer or processor at the boringmachine.

The boring tool is equipped with a down-hole electronics unit whichhouses a number of sensors, related circuitry, and preferably a batteryunit. The boring tool is provided with a beacon or sonde that producesan electromagnetic signal which may be detected using an above-groundtracker unit or receiver. Various sensors provided in the down-holeelectronics unit and elsewhere at the boring tool produce output signalswhich may be communicated to the tracker unit as a modulated boring toolsignal emitted by the sonde. Alternatively, boring tool sensor data maybe communicated to the boring machine via a drill string communicationlink and, if desired, from the boring machine to the tracker unit via awire or wireless communication link.

In one embodiment, the boring tool is provided with magnetic fieldsensors that sense variations in the magnetic field proximate the boringtool. The boring tool may further incorporate an antenna which issensitive to an electromagnetic signal produced aboveground, such as bythe tracker unit or a bore path target. The magnetic field sensors maybe incorporated in a magnetometer, which may be a multiple-axis (e.g.,three-axis) magnetometer. Such variations in the local magnetic fieldproximate the boring tool typically arise from the presence of nearbyferrous material within the earth, and may also arise from nearbycurrent carrying underground conductors. Iron-based metals within theearth, for example, may have significant magnetic permeability whichdistorts the earth's magnetic filed in the excavation area. Depending onthe particular mode of operation, such ferrous material may produceundesirable residual magnetic fields which can negatively affect theaccuracy of a given measurement if left undetected.

A magnetometer sense circuit of the boring tool may be sensitive to bothAC and DC fields. For example, magnetometer sense circuits that aresensitive to DC fields may be used for purposes of detecting changes inthe earth's magnetic field, typically resulting from the presence offerrous materials in the earth. Magnetometer sense circuits that aresensitive to AC fields may be used for purposes of detecting nearbyutilities.

The boring tool may further include a multiple-axis accelerometer, suchas a three-axis accelerometer. Examples of various sensor and instrumentarrangements which may be implemented within or proximate the boringtool are disclosed in U.S. Pat. Nos. 5,767,678; 5,764,062; 5,698,981;5,633,589; 5,469,155; 5,337,002; and 4,907,658; all of which are herebyincorporated herein by reference in their respective entireties.

A boring tool may be further equipped with an on-board radar unit, suchas a ground penetrating radar (GPR) unit. The boring tool may alsoinclude one or more geophysical sensors, including a capacitive sensor,acoustic sensor, ultrasonic sensor, seismic sensor, resistive sensor,and electromagnetic sensor, for example. One state-of-the-art GPR systemwhich may be incorporated into boring tool housings of varying sizes isimplemented in an integrated circuit package. Use of a down-hole GPRsystem provides for the detection of nearby buried obstacles andutilities, and characterization of the local geology. Some or all of theGPR data may be processed by a signal processor provided within theboring tool or by/in combination with an above-ground signal processor,such as a signal processor provided in a hand-held or otherwise portabletracker unit or, alternatively, a signal processor provided at theboring machine. The GPR unit may alternatively be provided in thehand-held/portable tracker unit or in both the boring tool and thehand-held/portable tracker unit.

By way of example, a ground penetrating radar integrated circuit (IC) orchip may be employed as part of the down-hole electronics. The GP-radarIC may be employed to perform subsurface surveying, object detection andavoidance, geologic imaging, and geologic characterization, for example.The GP-radar IC may implement several different detection methodologies,several of which will be describe hereinbelow. A suitable GP-radar IC ismanufactured by the Lawrence Livermore National Laboratory and isidentified as the micropower-impulse radar (MIR). The MIR device is alow cost radar system on a chip that uses conventional electroniccomponents. The radar transmitter and receiver are contained in apackage measuring approximately two square inches. The microradar isexpected to be further reduced to the size of a silicon microchip. Othersuitable radar IC's and detection methodologies are disclosed in U.S.Pat. Nos. 5,805,110; 5,774,091; and 5,757,320, which are herebyincorporated herein by reference in their respective entireties.

A microprocessor may also be provided as part of the down-holeelectronics. The microprocessor represents a circuit or device which iscapable of coordinating the activities of the various down-holeelectronic devices and instruments and may also provide for theprocessing of signals and data acquired at the boring tool. It isunderstood that the microprocessor may constitute or incorporate amicrocontroller, a digital signal processor (DSP), analog signalprocessor or other type of data or signal processing device. Moreover,the microprocessor may be configured to perform rudimentary, moderatelycomplex or highly sophisticated tasks depending on a given systemconfiguration or application. By way of example, a more sophisticatedsystem configuration may involve local signal processing of sensor dataacquired by one or more of the accelerometers, magnetometers, GP-radarIC, and/or other geophysical and environmental sensors provided at theboring tool.

Another relatively sophisticated boring tool system deployment mayinvolve the acquisition of various down-hole sensor data, production ofcontrol signals that control the boring operation, and comparison of apre-planned bore plan loaded into memory accessed by the down-holemicroprocessor with the actual bore path as indicated by the on-boarddown-hole sensors. The microprocessor may also incorporate or otherwisecooperate with a signal processing device to process GPR data acquiredby the GP-radar IC and other data acquired by thegeophysical/environmental sensors. The processed GPR andgeophysical/environmental data may be transmitted to an abovegrounddisplay unit for evaluation by an operator.

In one embodiment, a portable tracker unit comprises a groundpenetrating radar (GPR) unit. According to this embodiment, the boringtool includes a receiver and a signal processing device. The boring toolreceiver receives a probe signal transmitted by the GPR unit, and thesignal processing device generates a boring tool signal in response tothe probe signal. The boring signal according to this embodiment has acharacteristic that differs from the probe signal in one of timing,frequency content, information content, or polarization. Cooperationbetween the probe signal transmitter provided at the tracker unit andthe signature signal generating device provided at the boring toolresults in accurate detection of the boring tool location and, ifdesired, orientation, despite the presence of a large background signal.The GPR unit may also implement conventional subsurface imagingtechniques for purposes of detecting the boring tool and buriedobstacles. Various techniques for determining the position and/ororientation of a boring tool and for characterizing subsurface geologyusing a ground penetrating radar approach are disclosed in commonlyassigned U.S. Pat. Nos. 5,720,354 and 5,904,210, both of which arehereby incorporated herein by reference in their respective entireties.

An exemplary approach for detecting an underground object anddetermining the range of the underground object involves the use of atransmitter, which is coupled to an antenna, that transmits afrequency-modulated probe signal at each of a number of center frequencyintervals or steps. A receiver, which is coupled to the antenna whenoperating in a monostatic mode or, alternatively, to a separate antennawhen operating in a bistatic mode, receives a return signal from atarget object resulting from the probe signal. Magnitude and phaseinformation corresponding to the object are measured and stored in amemory at each of the center frequency steps. The range to the object isdetermined using the magnitude and phase information stored in thememory. This swept-step radar technique provides for high-resolutionprobing and object detection in short-range applications, and isparticularly useful for conducting high-resolution probing ofgeophysical surfaces and underground structures. A radar unit providedas part of an aboveground tracker unit or in-situ the boring tool mayimplement a swept-step detection methodology as described in U.S. Pat.No. 5,867,117, which is hereby incorporated herein by reference in itsentirety.

A gas detector may also be incorporated on or within the boring toolhousing and/or a backreamer which is coupled to the drill stringsubsequent to excavating a pilot bore. The gas detector may be used todetect the presence of various types of potentially hazardous gassources, including methane and natural gas sources. Upon detecting sucha gas, drilling may be halted to further evaluate the potential hazard.The location of the detected gas may be identified and stored to ensurethat the potentially hazardous location is properly mapped andsubsequently avoided.

The boring tool down-hole sensor unit may also include one or moretemperature sensors which sense the ambient temperature within theboring tool housing and/or each of the down-hole sensors and associatedcircuits. Using several temperature sensors provides for the computationof an average ambient temperature and/or average sensor temperature. Thetemperature data acquired using the temperature sensors may be used tocompensate for temperature related accuracy deviations that affect agiven down-hole sensor. Detection of an appreciable change intemperature, such as an appreciable increase in boring tool temperature,for example, may result in an increase in the sampling/acquisition rateof data obtained from the various down-hole sensor data in order tobetter characterize and compensate for temperature related affects onthe acquired data.

The data acquired by the various down-hole sensors, and, if applicable,the GPR unit and other geophysical sensors are transmitted to acontroller at the boring machine, the controller interchangeablyreferred to herein as a central processor. The central processor may beimplemented using a single processor or multiple processors at theboring machine. Alternatively, the central processor may be locatedremotely from the boring system, such as at a distantly located centralprocessing location or multiple remote processing locations. In oneembodiment, satellite, microwave or other form of high-speedtelecommunication may be employed to effect the transmission of sensordata, control signals, and other information between a remotely situatedcentral processor and the boring machine/boring tool components of areal-time boring control system.

The central processor processes the received boring tooltelemetry/GPR/geophysical sensor data and data associated with boringmachine activities during the drilling operation, such as dataconcerning pump pressures, motor speeds, pump/motor vibration, engineoutput, and the like. In certain embodiments, a real-time controlmethodology of the present invention provides for the elimination of thelocator operator and, in another embodiment, may further provide adown-range operator of the boring system with status information and atotal or partial control capability via a hand-held or otherwise mobileremote control facility.

Using the various sensor data, and preferably using data representativeof a pre-planned bore path, the central processor computes any neededboring tool course changes and boring machine operational changes inreal-time so as to maintain the boring tool on the pre-planned bore pathand at an optimal level of boring tool productivity. The centralprocessor may make gross and subtle adjustments to a boring operationbased on various other types of acquired data, including, for example,geophysical data at the drilling site acquired prior to or during theboring operation, drill string/drill head/installation product data suchas maximum bend radii and stress/strain data, and the location and/ortype of buried obstacles (e.g., utilities) and geology detected duringthe boring operation, such as that obtained by use of a down-hole orabove-ground GPR unit or geophysical sensor.

In the case of a detected buried obstacle or undesirable soil/rockcondition (e.g., hard rock or soft rock), the central processor mayeffect “on-the-fly” deviations in the actual boring tool excavationcourse by recomputing a valid alternative bore plan. On-the-flydeviations in actual boring tool heading may also be effected directlyby the operator. In response to such deviations, the central processorcomputes an alternative bore plan which preferably provides for safebypassing of such an obstruction/soil condition while passing as closeas possible through the targets established for the original pre-plannedbore path. Any such course deviation is communicated visually and/oraudibly to the operator and recorded as part of an “as-built” bore pathdata set. If an acceptable alternative bore plan cannot be computed dueto operational or safety constraints (e.g., maximum drill string bendradius will be exceeded or clearance from detected buried utility isless than pre-established minimum clearance margin), the drillingoperation is halted and a suitable warning message is communicated tothe operator.

Boring productivity is further enhanced by controlling the delivery offluid, such as a mud and water mixture or an air and foam mixture, tothe boring tool during excavation. The central processor, typically incooperation with a machine controller, controls various fluid deliveryparameters, such as fluid volume delivered to the boring tool and fluidpressure and temperature for example. The central processor may alsomonitor and adjust the viscosity of the fluid delivered to the boringtool, as well as the composition of the fluid. For example, the centralprocessor may modify fluid composition by controlling the type andamount of solid or slurry material that is added to the fluid. Thecomposition of the fluid delivered to the boring tool may be selectedbased on the composition of soil/rock subjected to drilling andappropriately modified in response to encountering varying soil/rocktypes at a given boring site.. Additionally, the composition of thefluid may be selected based upon the drill string rotation torque orthrust/pullback force.

The central processor may further enhance boring productivity bycontrolling the configuration of the boring tool according to soil/rocktype and boring tool steering/productivity requirements. One or moreactuatable elements of the boring tool, such as controllable plates,duckbill, cutting bits, fluid jets, and other earth engaging/penetratingportions of the boring tool, may be controlled to enhance the steeringand cutting characteristics of the boring tool. In an embodiment thatemploys an articulated drill head, the central processor may modify thehead position, such as by communicating control signals to a steppermotor that effects head rotation, and/or speed of the cutting heads toenhance the steering and cutting characteristics of the articulateddrill head. The pressure and volume of fluid supplied to a fluid hammertype boring tool, which is particularly useful when drilling throughrock, may be modified by the central processor. The central processorensures that modifications made to alter the steering and cuttingcharacteristics of the boring tool do not result in compromising drillstring, boring tool, installation product, or boring machine performancelimitations.

An adaptive steering mode of operation provides for the activemonitoring of the steerability of the boring tool within the soil/rocksubjected to drilling. The steerability factor indicates how quickly thedrill head can effect steering changes in a particular soil/rockcomposition, and may be expressed in terms of rate of change of pitch oryaw as the drill head moves longitudinally. If, for example, thesoil/rock steerability factor indicates that the actual drill stringcurvature will be flatter than the planned curvature, the centralprocessor may alter the pre-planned bore path so that the more desirablebore path is followed while ensuring that critical underground targetsare drilled to by the drill head. The steerability factor may bedynamically determined and evaluated during a boring operation.

Historical and current steerability factor data may thus be acquiredduring a given drilling operation and used to determine whether or not agiven bore path should be modified. A new bore path may be computed ifdesired or required using the historical and current steerability factordata. The adaptive steering mode may also consider factors such asutility/obstacle location, desirable safety clearance around utilitiesand obstacles, allowable drill string and product bend radius, andminimum ground cover and maximum allowable depth when altering thepre-planned bore path.

Another embodiment of the present invention provides an operator withthe ability to control all or a sub-set of boring system functions usinga remote control facility. According to this embodiment, an operatorinitiates boring machine and boring tool commands using a portablecontrol unit. Boring machine/tool status information is acquired anddisplayed on a graphics display provided on the portable control unit.The portable control unit may also embody the drill head locatingreceiver and/or the radio that transmits data to the boring machinereceiver/display. As will be discussed in greater detail, varyingdegrees of functionality may be built into the portable control unit,boring tool electronics package, and boring machine controllers toprovide varying degrees of control by each of these components. By wayof example, one system embodiment employs a conventional sonde-typetransmitter in the boring tool and a remote control unit that employs atraditional methodology for locating the boring tool. A GlobalPositioning System (GPS) unit or laser unit may also be incorporatedinto the remote control unit to provide a comparison between actual andpredetermined boring tool/operator locations. Using the locationinformation acquired using conventional locator techniques, an operatormay use the remote control unit to transmit control and steering signalsto the boring machine to effect desired alterations to boring toolproductivity and steering. By way of further example, the boring toolmay be equipped with a relatively sophisticated down-hole sensor unitand a local control and data processing capability. According to thissystem configuration, the remote control unit transmits control and/orsteering signals to the boring tool, rather than to the boring machine,to control drilling productivity and direction.

The down-hole sensor unit at the boring tool may produce various controlsignals in response to the data and the signals received from the remotecontrol unit. The control signals are transmitted to the boring machineto effect the necessary changes to boring machine/boring tooloperations. It will be appreciated that, using the various hardware,software, sensor, and machine components described herein, a largenumber of boring machine system configurations may be implemented. Thedegree of sophistication and functionality built into each systemcomponent may be tailored to meet a wide variety of excavation andgeologic surveying needs.

Referring now to FIG. 1, FIG. 1 illustrates a cross-section through aportion of ground where a boring operation takes place. The undergroundboring system, generally shown as the machine 12, is situatedaboveground 11 and includes a platform 14 on which is situated a tiltedlongitudinal member 16. The platform 14 is secured to the ground by pins18 or other restraining members in order to prevent the platform 14 frommoving during the boring operation. Located on the longitudinal member16 is a thrust/pullback pump 17 for driving a drill string 22 in aforward, longitudinal direction as generally shown by the arrow. Thedrill string 22 is made up of a number of drill string members 23attached end-to-end. Also located on the tilted longitudinal member 16,and mounted to permit movement along the longitudinal member 16, is arotation motor or pump 19 for rotating the drill string 22 (illustratedin an intermediate position between an upper position 19 a and a lowerposition 19 b). In operation, the rotation motor 19 rotates the drillstring 22 which has a boring tool 24 attached at the end of the drillstring 22.

A typical boring operation takes place as follows. The rotation motor 19is initially positioned in an upper location 19 a and rotates the drillstring 22. While the boring tool 24 is rotated, the rotation motor 19and drill string 22 are pushed in a forward direction by thethrust/pullback pump 17 toward a lower position into the ground, thuscreating a borehole 26. The rotation motor 19 reaches a lower position19 b when the drill string 22 has been pushed into the borehole 26 bythe length of one drill string member 23. A new drill string member 23is then added to the drill string 22 either manually or automatically,and the rotation motor 19 is released and pulled back to the upperlocation 19 a. The rotation motor 19 is used to thread the new drillstring member 23 to the drill string 22, and the rotation/push processis repeated so as to force the newly lengthened drill string 22 furtherinto the ground, thereby extending the borehole 26. Commonly, water orother fluid is pumped through the drill string 22 by use of a mud orwater pump. If an air hammer is used, an air compressor is used to forceair/foam through the drill string 22. The water/mud or air/foam flowsback up through the borehole 26 to remove cuttings, dirt, and otherdebris. A directional steering capability is typically provided forcontrolling the direction of the boring tool 24, such that a desireddirection can be imparted to the resulting borehole 26.

In accordance with one embodiment, a down-hole sensor unit of the boringtool 24 is communicatively coupled to the central processor 25 of theboring machine 12 through use of a communication link established viathe drill string 22. The communication link may be a co-axial cable, anoptical fiber or some other suitable data transfer medium extendingwithin and along the length of the drill string 22. The communicationlink may alternatively be established using a free-space link forinfrared or microwave communication or an acoustic telemetry approachexternal to the drill string 22. Communication of information betweenthe boring tool 24 and the central processor 25 may also be facilitatedusing a mud pulse technique as is known in the art.

According to another embodiment, the communication link establishedbetween the boring tool and the central processor via the drill stringcomprises an electrical conductor integral with each connected drillstem of the drill string. FIG. 18 shows generally at 388 a longitudinalcross sectional view of portions of drill stems 340 and 340′mechanically coupled at mechanical coupling point 359″. Drill stems 340and 340′ include outer surfaces 408 and 410, respectively, and innersurfaces defining hollow passages 390 and 392, respectively. The firstdrill stem 340 includes a segment of electrical conductor 394 that isencapsulated in an electrically insulative material. Likewise, thesecond drill stem 340′ also includes a segment of electrical conductor396 that is encapsulated in an electrically insulative material. Thefirst drill stem 340 includes a conductive ring 398 disposed at one end.Adjacent to the conductive ring 398, the first drill stem 340 alsoincludes an insulative (non-electrically-conductive) ring 404. Thesecond drill stem 340′ also includes a conductive ring 400, and aninsulative ring 406 disposed adjacently to the conductive ring 400.

When the second drill stem 340′ is mechanically coupled to the firstdrill stem 340 at mechanical coupling point 359″, an electrical contactpoint 402 is formed between the conductive rings 398 and 400. As thesecond drill stem 340′ is coupled to the first drill stem 340, theconductive ring 398 forms an electrical contact with the electricalconductor segment 394 disposed within the hollow passage 390. Likewise,the conductive ring 400 forms an electrical contact with the electricalconductor segment 396. Accordingly, a continuous electrical connectionis formed between the newly added second drill stem 340′ through theelectrically conductive coupling point 402 and mechanical coupling point359″ to the portion of the drill string 328 formed by the drill stem340, the starter rod (not shown) and the drill head (not shown).

The electrically insulative rings 404 and 406 electrically isolate theconductive rings 398 and 400, respectively, from the outer surfaces 408and 410, respectively, of the drill stems 340, 340′, respectively. Theelectrically insulative material encapsulating the electrical conductors394, 396 electrically isolate the electrical conductor segments 394, 396from the outer surfaces 408, 410, respectively. Additional embodimentsdirected to the use of integral electrical drill stem elements foreffecting communication of data between a boring tool and boring machineare disclosed in co-owned U.S. application Ser. No. 09/405,541, entitled“Apparatus and Method for Providing Electrical Transmission of Power andSignals in a Directional Drilling Apparatus,” filed on Sep. 24, 1999 andidentified as Attorney Docket No. 10646.247-US-01, which is herebyincorporated herein by reference in its entirety.

In accordance with another embodiment or the present invention, and withreference once again to FIG. 1, a tracker unit 28 may be employed toreceive an information signal transmitted from boring tool 24 which, inturn, communicates the information signal or a modified form of thesignal to a receiver situated at the boring machine 12. The boringmachine 12 may also include a transmitter or transceiver for purposes oftransmitting an information signal, such as an instruction signal, fromthe boring machine 12 to the tracker unit 28. In response to thereceived information signal, the tracker unit 28 may perform a desiredfunction, such as transmitting data or instructions to the boring tool24 for purposes of uplinking diagnostic or sensor data from the boringtool 24 or for adjusting a controllable feature of the boring tool 24(e.g., fluid jet orifice configuration/spray direction or cutting bitconfiguration/orientation). It is understood that transmission of suchdata and instructions may alternatively be facilitated through use of acommunication link established between the boring tool 24 and centralprocessor 25 via the drill string 22.

According to another embodiment, the tracker unit 28 may instead takethe form of a signal source for purposes of transmitting a targetsignal. The tracker unit 28 may be positioned at a desired location towhich the boring tool is intended to pass or reach. The boring tool maypass below the tracker unit 28 or break through the earth's surfaceproximate the tracker unit 28. The tracker unit 28 may emit anelectromagnetic signal which may be sensed by an appropriate sensorprovided within or proximate the boring tool 24, such as a magnetometerfor example. The central processor cooperates with the target signalsensor of the boring tool 24 to guide the boring tool 24 toward thetracker unit 28.

In one configuration, the tracker unit 28 may be incorporated in aportable unit which may be carried or readily moved by an operator. Theoperator may establish a target location by moving the portable trackerunit 28 to a desired aboveground location. The central processor, inresponse to sense signals received from the boring tool 24, controls theboring machine so as to guide the boring tool 24 in the direction of thetarget signal source. Alternatively, steering direction information canbe provided to an operator at the boring machine or remote from theboring machine by way of the central processor or remote unit to allowthe operator to make steering/control decisions.

FIG. 2 illustrates an important aspect of the present invention. Inparticular, FIG. 2 depicts various embodiments of a closed-loop controlsystem as defined between the boring machine 12 and the boring tool 24.According to one embodiment, communication of information between theboring machine 12 and the boring tool 24 is facilitated via the drillstring. A control loop, L_(A), illustrates the general flow ofinformation through a closed-loop boring control system according to afirst embodiment of the present invention. The down-hole sensor unit 27provided in the boring tool 24 provides location and orientation data.The acquired data may be processed locally within the down-hole sensorunit 27. The data acquired at the boring tool 24 is transmitted as aninformation signal along a first loop segment, L_(A-1), and is receivedby the boring machine 12. The received information signal is processedby the central processor 25 typically provided in a control unit 32 ofthe boring machine 12. Control signals that modify the direction andproductivity of the boring tool 24 may produced by at the boring machine12 or by the down-hole sensor unit 27.

In response to the processed information signal, desired adjustments aremade by the boring machine 12 to alter or maintain the activity of theboring tool 24, such adjustments being effected along a second loopsegment, L_(A-2), of the control loop, L_(A). It is noted that the firstloop segment, L_(A-1), typically involves the communication ofelectrical, electromagnetic, optical, acoustic or mud pulse signals,while the second loop segment, L_(A-2), typically involves thecommunication of mechanical/hydraulic forces. It is noted that thesecond loop segment, L_(A-2), may also involve the communication ofelectrical, electromagnetic or optical signals to facilitatecommunication of data and/or instructions from the central processor 25to the navigation package 27 of the boring tool 24.

In accordance with a second embodiment, a closed-loop control system isdefined between the boring machine 12, boring tool 24, and tracker unit28. A control loop, L_(B), illustrates the general flow of informationthrough this embodiment of a closed-loop control system of the presentinvention. The boring tool 24 transmits an information signal along afirst loop segment, L_(B-1), which is received by the tracker unit 28.In response to the received information signal, the tracker unit 28transmits an information signal along a second loop segment, L_(B-2),which is received by the central processor 25. The received informationsignal is processed by the central processor 25 of the boring machine12. In response to the processed information signal, desired adjustmentsare made by the boring machine 12 to alter or maintain the activity ofthe boring tool 24, such adjustments being effected along a third loopsegment, L_(B-3), of the control loop, L_(B). It is noted that the firstand second loop segments, L_(B-1), and L_(B-2), typically involve thecommunication of electrical, electromagnetic, optical, or acousticsignals, while the third loop segment, L_(B-3), typically involves thecommunication of mechanical/hydraulic forces. It is further noted thatthe third loop segment, L_(B-3), may also involve the communication ofelectrical, electromagnetic or optical signals to facilitatecommunication of data and/or instructions from the central processor 25to the navigation package 27 of the boring tool 24.

According to another embodiment, the control loop, L_(B), may providefor the initiation of control/steering signals at the tracker unit 28which may be received by either the boring machine 12 or the navigationelectronics 27 of the boring tool 24. It will be appreciated that thecomponents of the boring control system, the generation and processingof various control, steering, and target signals, and the flow ofinformation through the components may be selected and modified toaddress a variety of system and application requirements. As such, itwill be understood that the control loops depicted in FIG. 2 and otherfigures are provided for illustrating particular closed-loop controlmethodologies, and are not to be regarded as limiting embodiments. FIGS.15A and 15B, for example, illustrate other configurations of closed-loopcontrol system paths through the various system components, as will bediscussed in greater detail hereinbelow.

A control system and methodology according to the principles of thepresent invention provides for the acquisition and processing of boringtool location, orientation, and physical environment information (e.g.,temperature, stress/pressure, operating status), which may includegeophysical data, in real-time. Real-time acquisition and processing ofsuch information by the central processor 25 provides for real-timecontrol of the boring tool 24 and the boring machine 12. By way ofexample, a near-instantaneous alteration or halting of boring toolprogress may be effected by the central processor 25 via the closed-loopcontrol loops L_(A) or L_(B) depicted in FIG. 2 or other control loopupon detection of an unknown obstruction without experiencing delaysassociated with human observation and decision making.

It is believed that the latency associated with the acquisition andprocessing of boring tool signal information of a control loop definedbetween the boring machine 12 and the boring tool 24 is on the order ofmilliseconds. In certain applications, this latency may be in excess ofa second, but is typically less than two to three seconds. Such extendedlatencies may be reduced by using faster data communication andprocessing hardware, protocols, and software. In certain systemconfigurations which utilize above-ground receiver/transmitter units,the use of repeaters may significantly reduce delays associated withacquiring and processing information concerning the position andactivity of the boring tool 24. Repeaters may also be employed along acommunication link established through the drill stem.

In addition to the above characterization of the term “real-time” whichis expressed within a quantitative context, the term “real-time,” as itapplies to a closed-loop boring control system, may also becharacterized as the maximum duration of time needed to safely effect adesired change to a particular boring machine or boring tool operationgiven the dynamics of a given application, such as boring tooldisplacement rate, rotation rate, and heading, for example. By way ofexample, steering a boring tool which is moving at a relatively highrate of displacement so as to avoid an underground hazard requires afaster control system response time in comparison to steering the boringtool to avoid the same hazard at a relatively low rate of displacement.A latency of two, three or four seconds, for example, may be acceptablein the low displacement rate scenario, but would likely be unacceptablein the high displacement rate scenario.

In the context of the control loop configurations depicted in FIG. 2, itis believed that the delay associated with the acquisition andprocessing of boring tool signal information communicated along loopsegment L_(A-1) of loop L_(A) or along loop segments L_(B-1) and L_(B-2)of loop L_(B) and subsequent production of appropriate boringmachine/tool control signals by the central processor 25 of the boringmachine 12 is on the order of milliseconds and, depending on a givensystem deployment, may be on the order of microseconds. It can beappreciated that the responsiveness of the boring tool 24 to theproduced boring machine control signals (i.e., loop segments L_(A-2) orL_(B-3)) is largely dependent on the type of boring machine and toolemployed, soil/rock conditions, mud/water/foam/air flow rate andpressure, length of drill string, and operational characteristics of thevarious pumps and other mechanisms involved in the controlled rotationand displacement of the boring tool 24, all of which may be regarded ascumulative mechanical latency. Although such cumulative mechanicallatency will generally vary significantly, the mechanical latency for atypical drilling system configuration and drill stern length istypically on the order of a few seconds, such as about two to fourseconds.

With reference to FIGS. 3A-3E, five different control systemmethodologies for controlling a boring operation according to thepresent invention are illustrated. Concerning the embodiment depicted inFIG. 3A, the entry location of the boring tool into the subsurfacerelative to a reference is determined 550, such as by use of GPS or GRStechniques. The boring tool is thrust into the ground by the addition ofseveral drill rods to the boring tool/drill string. The boring tool ispushed away from the boring machine by a distance sufficient to preventmagnetic fields produced by the boring machine from perturbing theearth's magnetic field proximate the boring tool or from interferingwith the magnetic field sensors provided in the boring tool. The boringtool heading is then stabilized and initialized 552, such as by use of awalkover device.

Sensor data is acquired from the down-hole sensors of the boring tool.Any applicable up-hole sensor data, if available, is also acquired 556.Such up-hole sensor data may include, for example, drill roddisplacement data. Sensor data representative of the environmentalstatus at the boring tool (e.g., pressure, temperature, etc.) andgeophysical sensor data concerning the geology at the excavation site,such as underground structures, obstructions, and changes in geology,may also be acquired 558. Data concerning the operation of the boringmachine is also acquired 560. The position of the boring tool is thencomputed 562 based on boring tool heading data and the drill roddisplacement data.

Concerning the embodiment of FIG. 3B, the entry location is determined570 and the boring tool heading is stabilized and initialized 572.According to this embodiment, boring tool orientation data, such aspitch, yaw, and roll, is acquired 574 from the down-hole sensors. Anyapplicable up-hole sensor data is acquired 576, as is any availableenvironmental and geophysical sensor data 578. Data concerning theoperation of the boring machine is also acquired 580. The position ofthe boring tool is then computed 582 based on boring tool heading dataand the drill rod displacement data.

With regard to the embodiment of FIG. 3C, the entry location isdetermined 600 and the boring tool heading is stabilized and initialized602. Data representative of a change in the orientation or position ofthe boring tool is acquired 604 according to this embodiment. Forexample, the down-hole sensors may a change in boring tool orientationin terms of pitch, yaw, and roll. The orientation change data may betransmitted for aboveground processing. Applicable up-hole sensor data606, environmental/geophysical sensor data 608, and boring machineoperating data 610 may also be acquired. The position of the boring toolis then computed 612 based on the change of boring tool heading data andthe drill rod displacement data.

Concerning the embodiment of FIG. 3D, the entry location is determined620 and the boring tool heading is stabilized and initialized 622.According to this embodiment, data representative of the position of theboring tool is acquired 624, and the position of the boring tool iscomputed down-hole at the boring tool and transmitted for abovegroundprocessing. Applicable up-hole sensor data 626,environmental/geophysical sensor data 628, and boring machine operatingdata 630 may also be acquired. The boring tool position computeddown-hole may be improved on aboveground by recomputing 632 the boringtool position based on all relevant acquired data, such as drill roddisplacement data.

FIG. 3E illustrates an embodiment of a boring control system methodologyfor controlling boring machine and boring tool activities in accordancewith a successive approximation approach. Concerning the embodiment ofFIG. 3E, and with continued reference to FIG. 2, the starting locationof the bore, such as the bore entry point, is determined 40 with respectto a predetermined reference, such as by use of a GPS or GeographicReference System (GRS) facility. The displacement of the boring tool 24is computed and acquired 41 in real-time by use of a known technique,such as by monitoring the number of drill rods of known length added tothe drill string during the boring operation or by monitoring thecumulative length of drilling pipe which is thrust into the ground.

Boring tool sensor data is acquired during the boring operation inreal-time from various sensors provided in the down-hole sensor unit 27at the boring tool 24. Such sensors typically include a triad orthree-axis accelerometer, a three-axis magnetometer, and a number ofenvironmental and geophysical sensors. The acquired data is communicatedto the central processor 25 via the drill string communication link orvia the tracker unit 28.

Data concerning the orientation of the boring tool 24 is acquired 43 inreal-time using the sensors of the down-hole sensor unit 27 and/orthrough cooperative use of the tracker unit 28. The orientation datatypically includes the pitch, yaw, and roll (i.e., p, y, r) of theboring tool, although roll data may not be required. Depending on agiven application, it may also be desirable or required to acquire 44environmental data concerning the boring tool 24 in real-time, such asboring tool temperature and stress/pressure, for example. Geophysicaland/or geological data may also be acquired 46 in real-time. Dataconcerning the operation of the boring machine 12 is also acquired 47 inreal-time, such as pump/motor/engine productivity or pressure,temperature, stress (e.g., vibration), torque, speed, etc., dataconcerning mud/air/foam flow, composition, and delivery, and otherinformation associated with operation of the boring system 12.

The boring tool data, boring machine data, and other acquired data iscommunicated 48 to the central processor 25 of the boring machine 12.The central processor 25 computes 49 the location of the boring tool 24,preferably in terms of x-, y-, and z-plane coordinates. The locationcomputation is preferably based on the orientation of the boring tool 24and the change in boring tool position relative to the initial entrypoint or any other selected reference point. The boring tool location istypically computed using the acquired boring tool orientation data andthe acquired boring tool/drill string displacement data. Acquiringboring tool and machine data, transmitting this data to the centralprocessor 25, and computing the current boring tool position preferablyoccurs on a continuous or periodic real-time basis, as is indicated bythe dashed line 45.

The process of computing a current location of the boring tool,displacing the boring tool, sensing a change in boring tool position,and recomputing the current location of the boring tool on anincremental basis (e.g., successive approximation navigation approach)is repeated during the boring operation. A successive approximationnavigation approach within the context of the present inventionadvantageously obviates the need to temporarily halt boring toolmovement when performing a current boring tool location computation, asis require using conventional techniques. A walkover tracker or locatormay, however, be used in cooperation with the magnetometers of theboring tool to confirm the accuracy of the trajectory of the boring tooland/or bore path.

The computed location of the boring tool 24 is typically comparedagainst a pre-planned boring route to determine 50 whether the boringtool 24 is progressing along the desired underground path. If the boringtool 24 is deviating from the desired pre-planned boring route, thecentral processor 25 computes 52 an appropriate course correction andproduces control signals to initiate 54 the course correction inreal-time. In one particular embodiment, the navigation electronics ofthe boring tool 24 computes the course correction and produces controlsignals which are transmitted to the boring machine 12 to initiate 54the boring tool course correction.

If the central processor 25 determines 56 that the boring machine 12 isnot operating properly or within specified performance margins, thecentral processor 25 attempts to determine 58 the source of theoperational anomaly, determines 59 whether or not the anomaly iscorrectable, and further determines 61 whether or not the anomaly willdamage the boring machine 12, boring tool 24 or other component of theboring system. For example, the central processor 25 may determine thatthe rotation pump is operating beyond a preestablished pressurethreshold. The central processor 25 determines a resolution to theanomalous operating condition, such as by producing a control signal toreduce the thrust/pullback pump pressure so as to reduce rotation pumppressure without a loss in boring tool rotational speed.

If the central processor 25 determines 59 that the operational anomalyis not correctable and will likely cause damage to a component of theboring system, the central processor 25 terminates 63 drillingactivities and alerts 65 the operator accordingly. If an uncorrectableanomalous condition will likely not cause damage to a boring systemcomponent, drilling activities continue and the central processor 25alerts 67 the operator as to the existence of the problem. If thecentral processor 25 determines that the operational anomaly iscorrectable, the central processor 25 determines the corrective action60 and adjusts 62 boring machine operations in real-time to correct theoperational anomaly. The processes depicted in FIG. 3E are repeated on acontinuous or periodic basis to facilitate real-time control of theboring tool 24 and boring system 12 during a boring operation.

Referring to FIG. 4, there is illustrated a block diagram of variouscomponents of a boring system that provide for real-time control of aboring tool in accordance with an embodiment of the present invention.In accordance with the embodiment depicted in FIG. 4, a boring machine70 includes a central processor 72 which interacts with a number ofother controls, sensors, and data storing/processing resources. Thecentral processor 72 processes boring tool location and orientation datacommunicated from the boring tool 81 via the drill string 86 or,alternatively, via the tracker unit 83 to a transceiver (not shown) ofthe boring machine 70. The central processor 72 may also receivegeographic and/or topographical data from an external geographicreference unit 76, which may include a GPS-type system (GlobalPositioning System), Geographic Reference System (GRS), ground-basedrange radar system, laser-based positioning system, ultrasonicpositioning system, or surveying system for establishing an absolutegeographic position of the boring machine 70 and boring tool 81.

A machine controller 74 coordinates the operation of various pumps,motors, and other mechanisms associated with rotating and displacing theboring tool 81 during a boring operation. The machine controller 74 alsocoordinates the delivery of mud/foam/air to the boring tool 81 andmodifications made to the mud/foam/air composition to enhance boringtool productivity. The central processor 72 typically has access to anumber of automated drill mode routines 71 and trajectory routines 69which may be executed as needed or desired. A bore plan database 78stores data concerning a pre-planned boring route, including thedistance and variations of the intended bore path, boring targets, knownobstacles, unknown obstacles detected during the boring operation,known/estimated soil/rock condition parameters, and boring machineinformation such as allowable drill string or product bend radius, amongother data.

The central processor 72 or an external computer may execute boreplanning software 78 that provides the capability to design and modify abore plan on-site. The on-site designed bore plan may then be uploadedto the bore plan database 78 for subsequent use. As will be discussed ingreater detail hereinbelow, the central processor 72 may execute boreplanning software and interact with the bore plan database 78 during aboring operation to perform “on-the-fly” real-time bore plan adjustmentcomputations in response to detection of underground hazards,undesirable geology, and operator initiated deviations from a plannedbore program.

A geophysical data interface 82 receives data from a variety ofgeophysical and/or geologic sensors and instruments that may be deployedat the work site and at the boring tool. The acquiredgeophysical/geologic data is processed by the central processor 72 tocharacterize various soil/rock conditions, such as hardness, porosity,water content, soil/rock type, soil/rock variations, and the like. Theprocessed geophysical/geologic data may be used by the central processor72 to modify the control of boring tool activity and steering. Forexample, the processed geophysical/geologic data may indicate thepresence of very hard soil/rock, such as granite, or very soft soil,such as sand. The machine controller 74 may, for example, use thisinformation to appropriately alter the manner in which thethrust/pullback and rotation pumps are operated so as to optimize boringtool productivity for a given soil/rock type.

By way of further example, the central processor 72 may monitor theactual bend radius of a drill string 86 during a boring operation andcompare the actual drill string bend radius to a maximum allowable bendradius specified for the particular drill string 86 in use or theproduct being installed. The machine controller 74 may alter boringmachine operation and, in addition or in the alternative, the centralprocessor 72 may compute an alternative bore path to ensure compliancewith the maximum allowable bend radius requirements of the drill stringin use or the product being installed. It is noted that pitch and yaware vectors, and that actual drill string bend radius is a function ofthe vector sum of the change in pitch and yaw over a thrust distance.Boring machine alterations made to address a drill string/productoverstressing condition should compute such alterations based on themagnitude and direction of the pitch and yaw vector sum over a givendistance of thrust.

The central processor 72 may monitor the actual drill string/productbend radius to compare to the pre-planned path and steering plan, andadapt future control signals to accommodate any limitations in thesteerability of the soil/rock strata. Additionally, the centralprocessor 72 may monitor the actual bend radius, steerability factor,geophysical data, and other data to predict the amount of bore pathstraightening that will occur during the backreaming operation.Predicted bore path straightening, backreamer diameter, bore pathlength, type/weight of product being installed, and desiredutility/obstacle safety clearance will be used to make alterations tothe pre-planned bore path. This information will also be used whenplanning a bore path on-thy-fly, in order to reduce the risk of strikingutilities/obstacles while backreaming.

The central processor 72 may also receive and process data transmittedfrom one or more boring tool sensors. Orientation, pressure, andtemperature information, for example, may be sensed by appropriatesensors provided in the boring tool 81, such as a strain gauge forsensing pressure. Such information may be encoded on the signaltransmitted from the boring tool 81, such as by modulating the boringtool signal with an information signal, or transmitted as an informationsignal separate from the boring tool signal. When received by thecentral processor 72, an encoded boring tool signal is decoded toextract the information signal content from the boring tool signalcontent. The central processor 72 may modify boring system operations ifsuch is desired or required in response to the sensor information.

It is to be understood that the central processor 72 depicted in FIG. 4and the other figures may, but need not, be implemented as a singleprocessor, computer or device. The functions performed by the centralprocessor 72 may be performed by multiple or distributed processors,and/or any number of circuits or other electronic devices. As wasdiscussed previously, all or some of the functions associated with thecentral processor may be performed from a remotely located processingfacility, such as a remote facility which controls the boring machineoperations via a satellite or other high-speed communications link. Byway of further example, the functionality associated with some or all ofthe machine controller 74, automated drill mode routines 71, trajectoryroutines 69, bore plan software/database 78, geophysical data interface82, user interface 84, and display 85 may be incorporated as part of thecentral processor 72.

With continued reference to FIG. 4, a user interface 84 provides forinteraction between an operator and the boring machine 70. The userinterface 84 includes various manually-operable controls, gauges,readouts, and displays to effect communication of information andinstructions between the operator and the boring machine 70. As is shownin FIG. 4, the user interface 84 may include a display 85, such as aliquid crystal display (LCD) or active matrix display, alphanumericdisplay or cathode ray tube-type display (e.g., emissive display), forexample. The user interface 84 may further include a Web/Internetinterface for communicating data, files, email, and the like between theboring machine and Internet users/sites, such as a central control siteor remote maintenance facility. Diagnostic and/or performance data, forexample, may be analyzed from a remote site or downloaded to the remotesite via the Web/Internet interface. Software updates, by way of furtherexample, may be transferred to the boring machine or boring toolelectronics package from a remote site via the Web/Internet interface.It is understood that a secured (e.g., non-public) communication linkmay also be employed to effect communications between a remote site andthe boring machine/boring tool.

The portion of display 85 shown in FIG. 4 includes a display 79 whichvisually communicates information concerning a pre-planned boring route,such as a bore plan currently in use or one of several alternative boreplans developed or under development for a particular site. During orsubsequent to a boring operation, information concerning the actualboring route is graphically presented on the display 77. When usedduring a boring operation, an operator may view both the pre-plannedboring route display 79 and actual boring route display 77 to assess theprogress and accuracy of the boring operation. Deviations in the actualboring route, whether user initiated or central processor initiated, maybe highlighted or otherwise accentuated on the actual boring routedisplay 77 to visually alert the operator of such deviations. An audiblealert signal may also be generated.

It is understood that the display of an actual bore path may besuperimposed over a pre-planned bore path and displayed on the samedisplay, rather than on individual displays. Further, the displays 77and 79 may constitute two display windows of a single physical display.It is also understood that any type of view may be generated as needed,such as a top, side or perspective view, such as view with respect tothe drill or the tip of the boring tool, or an oblique, isometric, ororthographic view, for example.

It can be appreciated that the data displayed on the pre-planned andactual boring route displays 79 and 77 may be used to construct an“as-built” bore path data set and a path deviation data set reflectiveof deviations between the pre-planned and actual bore paths. Theas-built data typically includes data concerning the actual bore path inthree dimensions (e.g., x-, y-, z-planes), entrance and exit pitlocations, diameter of the pilot borehole and backreamed borehole, allobstacles, including those detected previously to or during the boringoperation, water regions, and other related data. Geophysical/geologicaldata gathered prior, during or subsequent to the boring operation mayalso be included as part of the as-built data.

FIG. 5 is a block diagram of a system 100 for controlling, in real-time,various operations of a boring machine and a boring tool whichincorporates a down-hole sensor unit according to an embodiment of thepresent invention. With respect to control loop LA, the system 100includes an interface 73 that permits the system 100 to accommodatedifferent types of sensor packages 89, including packages thatincorporate magnetometers, accelerometer rate sensors, various boringtool geophysical/environmental instruments and sensors, and telemetrymethodologies. The interface 73 may comprise both hardware and softwareelements that may be modified, either adaptively or manually, to providecompatibility between the boring tool sensor and communicationscomponents and the central processor components of the boring system100. In one embodiment, the interface 73 may be adaptively configured toaccommodate the mechanical, electrical, and data communicationspecifications of the boring tool electronics. In this regard, theinterface 73 eliminates or significantly reduces technology dependenciesthat may otherwise require a multiplicity of specialized interfaces foraccommodating a corresponding multiplicity of boring toolconfigurations.

With respect to control loop L_(B), an interface 75 permits the system100 to accommodate different types of locator and tracking systems,walkover units, boring tool geophysical/environmental instruments andsensors, and telemetry methodologies. Like the interface 73 associatedwith control loop LA, the interface 75 may comprise both hardware andsoftware elements that may be modified, either adaptively or manually,to provide compatibility between the tracker unit/boring tool componentsand the central processor components of the boring system 100. Theinterface 75 may be adaptively configured to accommodate the mechanical,electrical, and data communication specifications of the tracker unitand/or boring tool electronics.

In accordance with another embodiment, the central processor 72 is showncoupled to a transceiver 110 and several other sensors and devices viathe interface 75 so as to define an optional control loop, L_(B).According to this alternative embodiment, the transceiver 110 receivestelemetry from the tracker unit 83 and communicates this information tothe central processor 72. The transceiver 110 may also communicatesignals from the central processor 72 or other process of system 100 tothe tracker unit 83, such as boring tool configuration commands,diagnostic polling commands, software download commands and the like. Inaccordance with one less-complex embodiment, transceiver 110 may bereplaced by a receiver capable of receiving, but not transmitting, data.

Using the telemetry data received from the down-hole sensor unit 89 atthe boring tool 81 and, if desired, drill string displacement data, thecentral processor 72 computes the range and position of the boring tool81 relative to a ground level or other pre-established referencelocation. The central processor 72 may also compute the absoluteposition and elevation of the boring tool 81, such as by use of knownGPS-like techniques. Using the boring tool telemetry data received fromthe tracker unit 83, the central processor 72 also computes one or moreof the pitch, yaw, and roll (p, y, r) of the boring tool 81. Depth ofthe boring tool may also be determined based on the strength of anelectromagnetic sonde signal transmitted from the boring tool. It isnoted that pitch, yaw, and roll may also be computed by the down-holesensor unit 89, alone or in cooperation with the central processor 72.Suitable techniques for determining the position and/or orientation ofthe boring tool 81 may involve the reception of a sonde-type telemetrysignal (e.g., radio frequency (RF), magnetic, or acoustic signal)transmitted from the down-hole sensor unit 89 of the boring tool 81.

In accordance with one embodiment, a mobile tracker apparatus may usedto manually track and locate the progress of the boring tool 81 which isequipped with a transmitter that generates a sonde signal. The tracker83, in cooperation with the central processor 72, locates the relativeand/or absolute location of the boring tool 81. Examples of such knownlocator techniques are disclosed in U.S. Pat. Nos. 5,767,678; 5,764,062;5,698,981; 5,633,589; 5,469,155; 5,337,002; and 4,907,658; all of whichare hereby incorporated herein by reference in their respectiveentireties. These systems and techniques may be advantageously adaptedfor inclusion in a real-time boring tool locating approach consistentwith the teachings and principles of the present invention.

A suitable technique for determining the position and/or orientation ofthe boring tool 81 using a handheld tracker unit involves the use ofaccelerometers and magnetometers incorporated in the down-hole sensorunit 89 of the boring tool 81. According to this embodiment, thedown-hole sensor unit 89 of the boring tool 81 is equipped with atriaxial magnetometer, a triaxial accelerometer, and a magnetic dipoleantenna for emitting an electromagnetic dipole field, the process ofwhich is disclosed in U.S. Pat. No. 5,585,726, which is herebyincorporated herein by reference in its entirety. Signals produced bythe triaxial magnetometer and triaxial accelerometer are transmittedfrom the boring tool 81 via the dipole antenna and received by thetracker unit 83 which processor the received signals or, alternatively,relays the signals to the transceiver 110 of the boring system. Thereceived signals are used by the central processor to compute theorientation and, using boring tool displacement data, the location ofthe boring tool 81, although the orientation of the boring tool 81 maybe computed directly by the tracker unit 83

The approximate position of the boring tool 81 may be computed during aboring operation by performing an integration of the signals over thedistance the boring tool 81 has traveled. The tracker unit 83, which istypically implemented as a portable or hand-held unit, continuouslyreceives telemetry signals from the boring tool transmitter by detectingthe electromagnetic dipole field emitted by the boring tool 81. Theactual position of the boring tool 81, as determined by using thelocator telemetry data, is used to correct for any integration errorthat may have been introduced into the integration computation. Inanother embodiment, boring tool position and orientation is detected bythe tracker unit 83. As such, the actual position of the boring tool 81may be computed by the tracker unit 83 rather than at the boring machinelocation. The location/orientation data is processed by the centralprocessor 72 to provide closed-loop control of the boring tool 81 duringa boring operation.

Yet another technique for determining the position and/or orientation ofthe boring tool 81 involves the use of a tracker unit 83 comprisingseveral spaced-apart antenna cells situated along one or both sides of apre-planned bore path. This embodiment advantageously obviates the needof a locator operator. A transmitter provided in the boring tool 81transmits a signal which is received by the antenna cell network. Theboring tool signal is relayed along the antenna cell links and isreceived by a transceiver coupled to the central processor 72 forprocessing by the central processor 72. The central processor 72computes the actual location of the boring tool 81 and compares theactual location with a pre-planned location according to a predeterminedunderground path stored in the bore plan database 78. The machinecontroller 74 initiates any required course correction, in real-time,resulting from a deviation between the actual and pre-planned boringtool locations. A system well-suited for use according to thisembodiment is the TRANSITRAK iGPS system manufactured by DigitalControls, Inc. of Renton, Wash. It will be appreciated that techniquesother than those described herein for determining boring tool locationand orientation may be employed to provide location and orientationsignals to the central processor 72 for purposes of controlling boringtool activity in a closed-loop, real-time operating environment.

In accordance with another embodiment of the present invention, locationunit 83 employs an apparatus that determines the location andorientation of the boring tool 81 by employment of a radar-like probeand detection technique. Suitable techniques for determining theposition and/or orientation of the boring tool 81 using a groundpenetrating radar approach are disclosed in commonly assigned U.S. Pat.Nos. 5,720,354 and 5,904,210, both of which are incorporated herein byreference in their respective entireties. The boring tool 83, accordingto this embodiment, is provided with a device which generates a specificsignature signal in response to a probe signal transmitted from thetracker unit 83. Cooperation between the probe signal transmitterprovided at the tracker unit 83 and the signature signal generatingdevice provided at the boring tool 81 results in accurate detection ofthe boring tool location and, if desired, orientation, despite thepresence of a large background signal.

Precision detection of the boring tool location and orientation enablesthe operator to accurately locate the boring tool during operation and,if provided with a directional capability, avoid buried obstacles suchas utilities and other hazards. The signature signal produced by theboring tool 81 may be generated either passively or actively, and may bea microwave or an acoustic signal. Further, the signature signal may beproduced in a manner which differs from that used to produce the probesignal in one or more ways, including timing, frequency content,information content, or polarization.

According to this embodiment, and with reference to FIG. 19, trackerunit 83 comprises a detection unit 228 which includes a receiver 256, adetector 258, and a signal processor 260. The receiver 256 receivesreturn signals from the ground 210 and communicates them to the detector258. The detector 258 converts the return signals into electricalsignals which are subsequently analyzed in the signal processing unit260. In a first embodiment in which a probe signal 236 produced bygenerator 252 constitutes a microwave signal, the receiver 256 typicallyincludes an antenna, and the detector 258 typically includes a detectiondiode. In a second embodiment in which the probe signal 236 constitutesan acoustic wave, the receiver 256 typically is a probe which makes goodmechanical contact with the ground 210 and the detector 258 includes asound-to-electrical transducer, such as microphone.

The signal processor 260 may include various preliminary components,such as a signal amplifier, a filtering circuit, and ananalog-to-digital converter, followed by more complex circuitry forproducing a two or three dimensional image of a subsurface volume whichincorporates the various underground obstructions 230 and the boringtool 81. The detection unit 228 may also contain a beaconreceiver/analyzer 261 for detecting and interpreting a signal receivedfrom an active beacon or sonde provided in the boring tool 81. Thesignal transmitted by the active beacon may include informationconcerning the orientation and/or the environment of the boring tool 81,which is decoded by the beacon receiver/analyzer 261.

The detection unit 228 also contains a decoder 263 for decodinginformation signal content that may be encoded on the signature signalproduced by the boring tool 81. Orientation, pressure, temperature, andgeophysical information, for example, may be sensed by appropriatesensors provided in the boring tool 81, such as a strain gauge forsensing pressure, a mercury switch for detecting orientation, a pitchsensor for measuring boring tool pitch, a GPR sub-system or one or moregeophysical sensors. Such information may be encoded on the signaturesignal, such as by modulating the signature signal with an informationsignal, or otherwise transmitted as part of, or separate from, thesignature signal. When received by the receiver 256, an encoded returnsignal is decoded by the decoder 261 to extract the information signalcontent from the signature signal content. It is noted that thecomponents of the detection unit 228 illustrated in FIG. 19 need not becontained within the same housing or supporting structure.

The detection unit 228 transmits acquired information along a datatransmission link to the central processor 72. The data transmissionlink is provided to handle the transfer of data between the detectionunit 228 of the tracker unit 83 and the transceiver of the boringsystem, and may be a co-axial cable, an optical fiber, a free-space linkfor infrared or microwave communication, or some other suitable datatransfer medium or technique.

A boring system of the present provides the opportunity to conduct aboring operation in a variety of different modes. By way of example, awalk-the-path mode of operation involves initially walking along adesired bore path and making a recordation of the desired path. Anoperator may use a hand-held GPS-type unit, for example, togeographically define the bore path. Alternatively, the operator may usea down-hole sensor unit similar to that used with the boring tool to mapthe desired bore path. Moreover, the operator may use the same down-holesensor unit as that used during the boring operation to establish thedesired bore path.

After walking the desired bore path, the stored bore path data may beuploaded to the central processor or to a PC which executes bore plansoftware to produce a machine usable bore plan. The hand-held unit mayalso be provided with data processing and display resources necessary toexecute bore plan software for purposes of producing a machine usablebore plan. The bore plan software allows the operator to further refineand modify a bore plan based on the previously acquired bore path data.The operator interacts with the bore plan software, as will be discussedin greater detail hereinbelow, to define the depth of the bore path,entry points, exit points, targets, and other features of the bore plan.Another mode of operation involves a so called walk-the-dog method bywhich an operator walks above the boring tool with a portable trackerunit. The tracker unit is provided with steering controls which allowthe operator to initiate boring tool steering changes as desired. Theboring tool, according to this embodiment, is provided with electronicswhich enables it to receive the steering commands transmitted by thetracker unit, compute, in-situ, appropriate steering control signals inresponse to the steering command, and transmit the steering commands tothe boring machine to effect the desired steering change. In thisregard, all boring tool steering changes are made by the down rangeoperator walking above the boring tool, and not by the boring machineoperator.

In accordance with yet another mode of boring machine operation, asteer-by-tool approach involves the transmission of a signal at anaboveground target along the bore path, it being understood that thesignal may be transmitted by an underground target. The boring tooldetects the target signal and computes, in-situ, the necessary steeringcommands to direct the boring tool to the target signal. Any steeringchanges that are necessary, such as deviations needed to avoidunderground obstructions or undesirable geology, are effected bysteering commands produced by the down-hole electronics. The boring toolelectronics computes the steering changes needed to successfully steerthe boring tool around the obstruction and to the target signal. Theboring tool electronics may execute bore plan software to recompute abore plan when changes to -the bore plan are required for reasons ofsafety or productivity.

According to another mode of operation, a smart-tool approach involvesdownloading a bore plan into the boring tool electronics. The boringtool electronics computes all steering changes needed to maintain theboring tool along the predetermined bore path. An operator, however, mayoverride a currently executing bore plan by terminating the drillingoperation at the boring machine of via a tracker unit. A new orreplacement bore plan may then be downloaded to the boring tool forexecution.

Turning now to FIG. 6, a bore plan database/software facility 78 may beaccessed by or incorporated into the central processor 72 for purposesof establishing a bore plan, storing a bore plan, and accessing a boreplan during a boring operation. A user, such as a bore plan designer orboring machine operator, may access the bore plan database 78 via a userinterface 84. In a configuration in which the central processor 72cooperates with a computer external to the boring machine, such as apersonal computer, the user interface 84 typically comprises a userinput device (e.g., keyboard, mouse, etc.) and a display. In aconfiguration in which the central processor 72 is used to execute thebore plan algorithms or interact with the bore plan database 78, theuser interface 84 comprises a user input device and display provided onthe boring machine or as part of the central processor housing.

A bore plan may be designed, evaluated, and modified efficiently andaccurately using bore plan software executed by the central processor72. Alternatively, a bore plan may be developed using a computer systemindependent of the boring machine and subsequently uploaded to the boreplan database 78 for execution and/or modification by the centralprocessor 72. Once established, a bore plan stored in the bore plandatabase 78 may be accessed by the central processor 72 for use during aboring operation. In general, a bore plan may be designed such that thedrill string is as short as possible. A bore should remain a safedistance away from underground utilities to avoid strikes. The drillpath should turn gradually so that stress on the drill string andproduct to be installed in the borehole is minimized. The bore planshould also consider whether a given utility requires a minimum groundcover.

A bore plan designer may enter various types of information to define aparticular bore plan. A designer initially constructs the generaltopography of a given bore site. In this context, topography refers to atwo-dimensional representation of the earth's surface which is definedin terms of distance and height values. Alternatively, the designer mayinitially construct the general topography of a given bore site in threedimensions. In this context, topography refers to a three-dimensionalrepresentation of the earth's surface.

The topography of a region of interest is established by entering aseries of two-dimensional points or, alternatively, three-dimensionalpoints. The bore plan software sorts the points based on distance, andconnects them with straight lines. As such, each topographical point hasa unique distance associated with it. The bore plan software determinesthe height of the surface for any distance between two topographicalpoints using linear interpolation between the nearest two points.Topography is used to set the scope (i.e., upper and lower distancebounds) of the graphical display. Establishing the topography providesfor the generation of a graphical representation of the bore site.

After establishing the topography, the bore plan designer selects areference origin, which corresponds to a distance, height, andleft/right value relative to a reference value, such as zero. Thedesigner may then select a reference line that runs through thereference origin. The reference line is typically established to be inthe general direction of the borehole, horizontal, and straight. Thedesigner may also enter the longitude, latitude, and altitude of thelocal reference origin and the bearing of the reference line to providedfor absolute geographic location determinations. Once the referencesystem is established, the designer can uniquely define a number ofthree-dimensional locations to define the bore path, including thedistance from the origin along the reference line in the positivedirection, the height above the reference line and origin, and locationsleft and right of the reference line in the positive distance direction.Direction may also be uniquely specified by entering an azimuth value,which refers to a horizontal angle to the left of the reference linewhen viewed from the origin facing in the positive distance direction,and a pitch value, which refers to a vertical angle above the referenceline.

Objects, such as existing utilities, obstructions, obstacles, waterregions, and the like, may be defined with reference to the surface ofthe earth. These points may be specified using a depth of object valuerelative to the earth surface and the height of the object. Thecharacteristics of the drill string rods, such as maximum bend radius,and of the product to be pulled through the borehole during abackreaming operation, such as a utility conduit, may be entered by thedesigner or obtained from a product configuration databases 102 as isshown in FIG. 5. Dimensions, maximum bend radii, material composition,and other characteristics of a given product may be considered duringthe bore path planning process. For example, the product pulled througha borehole during a backreaming operation will have a diameter greaterthan that of the pilot bore, and the product will often have bendingcharacteristics different from those associated with the drill stringrods. These and other factors may affect the size and configuration andcurvature of a given borehole, and as such, may be entered as input datainto the bore path plan. The designer may also input soil/rockcomposition and geophysical characteristics data associated with a givenbore site. Data concerning soil/rock hardness, composition, and the likemay be entered and subsequently considered by the bore plan software.

After entering all applicable objects associated with a desired borepath, the designer enters a number of targets through which the borepath will pass. Targets have an associated three-dimensional locationdefined by distance, left/right, and depth values that are entered bythe operator. The designer may optionally enter pitch and/or azimuthvalues at which the bore path should pass. The designer may also assignbend radius characteristics to a bore segment by entering values of themaximum bend radius and minimum bend radius sections for a destinationtarget.

Using the data entered by the bore plan designer and other stored dataapplicable to a given bore path plan, the central processor 72 connectseach target pair using course computations determined at steps separatedby a preestablished spacing, such as 25 cm spaced steps. At each step,the central processor 72 calculates the direction the bore path shouldtake so that the bore path passes through the next target withoutviolating any of the preestablished conditions. The central processor 72thus mathematically constructs the bore path in an incremental fashionuntil the exit pit location is reached. If a preestablished condition,such as drill rod bend radius, is violated, the error condition iscommunicated to the designer. The designer may then modify the bore planto satisfy the particular preestablished condition.

In a further embodiment, a preestablished bore plan may be dynamicallymodified during a boring operation upon detection of an unknown obstacleor upon boring through soil/rock which significantly degrades thesteering and/or excavation capabilities of the boring tool. Upondetecting either of these conditions, the central processor 72 attemptsto compute a “best fit” alternative bore path “on-the-fly” that passesas closely as possible to subsequent targets. Detection of anunidentified or unknown obstruction is communicated to the operator, aswell as a message that an alternative bore plan is being computed. Ifthe alternative bore plan is determined valid, then the boring tool isadvanced uninterrupted along the newly computed alternative bore path.If a valid alternative bore path cannot be computed, the centralprocessor 72 halts the boring operation and communicates an appropriatewarning message to the operator.

During a boring operation, as was discussed previously, bore plan datastored in the bore plan database 78 may be accessed by the centralprocessor 72 to determine whether an actual bore path is accuratelytracking the planned bore path. Real-time course corrections may be madeby the machine controller 74 upon detecting a deviation between theplanned and actual bore paths. The actual boring tool location may bedisplayed for comparison against a display of the preplanned boring toollocation, such as on the actual and pre-panned boring route displays 77and 79 shown in FIG. 4. As-built data concerning the actual bore pathmay be entered manually or automatically from data downloaded directlyfrom a tracker unit, such as from the tracker unit 83. Alternatively,as-built data concerning the actual bore path may be constructed basedon the trajectory information received from the navigation electronicsprovided at the boring tool 81. A bore plan design methodologyparticularly well-suited for use with the real-time central processor ofthe present invention is disclosed in co-owned U.S. Ser. No. 60/115,880entitled “Bore Planning System and Method,” filed Jan. 13, 1999, whichis hereby incorporated herein by reference in its entirety.

With continued reference to FIG. 5, the system 100 may include one ormore geophysical sensors 112, including a GPR imaging unit, a capacitivesensor, acoustic sensor, ultrasonic sensor, seismic sensor, resistivesensor, and electromagnetic sensor, for example. In accordance with oneembodiment, surveying the boring site, either prior to or during theboring operation, with geophysical sensors 112 provides for theproduction of data representative of various characteristics of theground medium subjected to the survey. The ground characteristic dataacquired by the geophysical sensors 112 during the survey may beprocessed by the central processor 72, which may modify boring machineactivities in order to optimize boring tool productivity given thegeophysical makeup of the soil/rock at the boring site.

The central processor 72 receives data from a number of geophysicalinstruments which provide a physical characterization of the geology fora particular boring site. The geophysical instruments may be provided onthe boring machine, provide in one or more instrument packs separatefrom the boring machine or provided in, on, or proximate the boring tool81. A seismic mapping instrument, from example, represents an electronicdevice consisting of multiple geophysical pressure sensors. A network ofthese sensors may be arranged in a specific orientation with respect tothe boring machine, with each sensor being situated so as to make directcontact with the ground. The network of sensors measures ground pressurewaves produced by the boring tool 81 or some other acoustic source.Analysis of ground pressure waves received by the network of sensorsprovides a basis for determining the physical characteristics of thesubsurface at the boring site and also for locating the boring tool 81.These data are processed by the central processor 72.

A point load tester represents another type of geophysical sensor 112that may be employed to determine the geophysical characteristics of thesubsurface at the boring site. The point load tester employs a pluralityof conical bits for the loading points which, in turn, are brought intocontact with the ground to test the degree to which a particularsubsurface can resist a calibrated level of loading. The data acquiredby the point load tester provide information corresponding to thegeophysical mechanics of the soil/rock under test. These data may alsobe transmitted to the central processor 72.

Another type of geophysical sensor 112 is referred to as a Schmidthammer which is a geophysical instrument that measures the reboundhardness characteristics of a sampled subsurface geology. Othergeophysical instruments 112 may also be employed to measure the relativeenergy absorption characteristics of a rock mass, abrasivity, rockvolume, rock quality, and other physical characteristics that togetherprovide information regarding the relative difficulty associated withboring through a given geology. The data acquired by the Schmidt hammerare also received and processed by the central processor 72.

As is shown in FIGS. 5 and 7, a machine controller 74 is coupled to thecentral processor 72 and modifies boring machine operations in responseto control signals received from the central processor 72.Alternatively, some or all of the machine controller functionality maybe integrated into and/or performed by the central processor 72. As isbest shown in FIG. 7, the machine controller 74 controls a rotation pumpor motor 146, referred to hereinafter as a rotation pump, that rotatesthe drill string during a boring operation. The machine controller 74also controls the rotation pump 146 during automatic threading of rodsto the drill string. A pipe loading controller 141 may be employed tocontrol an automatic rod loader apparatus during rod threading andunthreading operations. The machine controller 74 also controls athrust/pullback pump or motor 144, referred to hereinafter as athrust/pullback pump. The machine controller 74 controls thethrust/pullback pump 144 during boring and backreaming operations tomoderate the forward and reverse displacement of the boring tool.

The thrust/pullback pump 144 depicted in FIG. 8 drives a hydrauliccylinder 154, or a hydraulic motor, which applies an axially directedforce to a length of pipe 180 in either a forward or reverse axialdirection. The thrust/pullback pump 144 provides varying levels ofcontrolled force when thrusting a length of pipe 180 into the ground tocreate a borehole and when pulling back on the pipe length 180 whenextracting the pipe 180 from the borehole during a back reamingoperation. The rotation pump 146, which drives a rotation motor 164,provides varying levels of controlled rotation to a length of the pipe180 as the pipe length 180 is thrust into a borehole when operating theboring machine in a drilling mode of operation, and for rotating thepipe length 180 when extracting the pipe 180 from the borehole whenoperating the boring machine in a back reaming mode. Sensors 152 and 162monitor the pressure of the thrust/pullback pump 144 and rotation pump146, respectively.

The machine controller 74 also controls rotation pump movement whenthreading a length of pipe onto a drill string 180, such as by use of anautomatic rod loader apparatus of the type disclosed in commonlyassigned U.S. Pat. No. 5,556,253, which is hereby incorporated herein byreference in its entirety. An engine or motor (not shown) providespower, typically in the form of pressure, to both the thrust/pullbackpump 144 and the rotation pump 146, although each of the pumps 144 and146 may be powered by separate engines or motors.

In accordance with one embodiment for controlling the boring machineusing a closed-loop, real-time control methodology of the presentinvention, overall boring efficiency may be optimized by appropriatelycontrolling the respective output levels of the rotation pump 146 andthe thrust/pullback pump 144. Under dynamically changing boringconditions, closed-loop control of the thrust/pullback and rotationpumps 144 and 146 provides for substantially increased boring efficiencyover a manually controlled methodology. Within the context of ahydrostatically powered boring machine or, alternatively, one powered byproportional valve-controlled gear pumps or electric motors, increasedboring efficiency is achievable by rotating the boring tool 181 at aselected rate, monitoring the pressure of the rotation pump 146, andmodifying the rate of boring tool displacement in an axial directionwith respect to an underground path while concurrently rotating theboring tool 181 at the selected output level in order to compensate forchanges in the pressure of the rotation pump 146. Sensors 152 and 162monitor the pressure of the thrust/pullback pump 144 and rotation pump146, respectively.

In accordance with one mode of operation, an operator initially sets arotation pump control to an estimated optimum rotation setting during aboring operation and modifies the setting of a thrust/pullback pumpcontrol in order to change the gross rate at which the boring tool 181is displaced along an underground path when drilling or back reaming.The rate at which the boring tool 181 is displaced along the undergroundpath during drilling or back reaming typically varies as a function ofsoil/rock conditions, length of drill pipe 180, fluid flow through thedrill string 180 and boring tool 181, and other factors. Such variationsin displacement rate typically result in corresponding changes inrotation and thrust/pullback pump pressures, as well as changes inengine/motor loading. Although the rotation and thrust/pullback pumpcontrols permit an operator to modify the output of the thrust/pullbackand rotation pumps 144 and 146 on a gross scale, those skilled in theart can appreciate the inability by even a highly skilled operator toquickly and optimally modify boring tool productivity under continuouslychanging soil/rock and loading conditions.

After initially setting the rotation pump control to the estimatedoptimum rotation setting for the current boring conditions, an operatorcontrols the gross rate of displacement of the boring tool 181 along anunderground path by modifying the setting of the thrust/pullback pumpcontrol. During a drilling or back reaming operation, the rotation pumpsensor 162 monitors the pressure of the rotation pump 146, andcommunicates rotation pump pressure information to the machinecontroller 74. The rotation pump sensor 162 may alternativelycommunicate rotation motor speed information to the machine controller74 in a configuration which employs a rotation motor rather than a pump.Excessive levels of boring tool loading during drilling or back reamingtypically result in an increase in the rotation pump pressure, or,alternatively, a reduction in rotation motor speed.

In response to an excessive rotation pump pressure or, alternatively, anexcessive drop in rotation rate, the machine controller 74 communicatesa control signal to the thrust/pullback pump 144 resulting in areduction in thrust/pullback pump pressure so as to reduce the rate ofboring tool displacement along the underground path. The reduction inthe force of boring tool displacement decreases the loading on theboring tool 181 while permitting the rotation pump 146 to operate at anoptimum output level or other output level selected by the operator.

It will be understood that the machine controller 74 may optimize boringtool productivity based on other parameters, such as torque imparted tothe drill string via the rotation pump 146. For example, the operatormay select a desired rotation and thrust/pullback output for aparticular boring operation. The machine controller 74 monitors thetorque imparted to the drill string at the gearbox and modifies one orboth of the rotation and thrust/pullback pumps 146, 144 so that thedrill string torque does not exceed a pre-established limit.

The phenomenon of drill string buckling may also be detected andaddressed by the machine controller 74 when controlling a boringoperation. Drill string buckling typically occurs in soft soils and isassociated with movement of the gearbox and the contemporaneous absenceof boring tool movement in a longitudinal direction. Appreciablemovement of the gearbox and a detected lack of appreciable longitudinalmovement of the boring tool may indicate the occurrence of undesirabledrill string buckling. The machine controller 74 may monitor gearboxmovement and longitudinal movement of the boring tool in order to detectand correct for drill string buckling.

The machine controller 74 further moderates the pullback force during abackreaming operation to avoid overstressing the installation productbeing pulled back through the borehole. Strain or force measuringdevices may be provided between the backreamer and the installationproduct to measure the pullback force experienced by the installationproduct. Strain/force sensors may also be situated on the productitself. The machine controller 74 may modify the operation of thethrust/pullback pump 144 to ensure that the actual product stress level,as indicated by the strain/force sensors, does not exceed apre-established threshold.

The machine controller 74 may also control the pressure of the rotationpump 146 in both forward and reverse (e.g., clockwise andcounterclockwise) directions. When drilling through soil or rock, themachine controller 74 controls the rotation pump pressure tocontrollably rotate the drill string/boring tool in a first directionduring cutting and steering operations. The machine controller 74 alsocontrols the rotation pump pressure to controllably rotate the drillstring in a second direction so as to prevent unthreading of the drillstring. Preventing unthreading of the drill string is particularlyimportant when cutting with rock boring heads that require a rockingaction for improved productivity.

Another system capability involves the detection of utility/obstaclepunctures or penetration events. An appreciable drop in thrust and/orrotation pump pressure may occur when the boring tool passes through autility, in comparison to pump pressures experienced prior to and afterstriking the utility. If an appreciable drop in thrust and/or rotationpump pressure is detected, the machine controller 74 may halt drillingoperations and alert the operator as to the possible utility contactevent. The machine controller 74 may further monitor thrust and/orrotation pump pressure for pressure spikes followed by a drop in thrustand/or rotation pump pressure, which may also indicate the occurrence ofa utility contact event.

The high speed response capability of the machine controller 74 incooperation with the central processor 72 provides for real-timeautomatic moderation of the operation of the boring machine undervarying loading conditions, which provides for optimized boringefficiency, reduced detrimental wear-and-tear on the boring tool 181,drill string 180, and boring machine pumps and motors, and reducedoperator fatigue by automatically modifying boring machine operations inresponse to both subtle and dramatic changes in soil/rock and loadingconditions. An exemplary methodology for controlling the displacementand rotation of a boring tool which may be adapted for use in aclosed-loop control approach consistent with the principles of thepresent invention is disclosed in commonly assigned U.S. Pat. No.5,746,278, which is hereby incorporated herein by reference in itsentirety.

With continued reference to FIG. 8, a vibration sensor 150, 160 may becoupled to each of the thrust/pullback pump 144 and rotation pump 146for purposes of monitoring the magnitude of pump vibration thattypically occurs during operation. Other vibration sensors (not shown)may be mounted to the chassis or other structure for purposes ofdetecting displacement or rotation of the boring system chassis or highlevels of chassis vibration during a boring operation. It is appreciatedby the skilled boring machine operator that pump/motor/chassis vibrationis a useful sensory input that is often considered when manuallycontrolling the boring machine.

Changes in the magnitude of pump/chassis vibration as felt by theoperator is typically indicative of a change in pump loading orpressure, such as when the boring tool is passing through cobblestone.Pump/motor/chassis vibration, which has heretofore been ignored inconventional control schemes, may be monitored using pump vibrationsensors 150, 160 and one or more chassis vibration sensors, converted tocorresponding electrical signals, and communicated to respectivethrust/pullback and rotation controllers 124, 126. The transducedpump/chassis vibration data may be transmitted to the machine controller74 and used to adjust the output of the thrust/pullback and rotationpumps 144, 146.

By way of example, a vibration threshold may be established usingempirical means for each of the thrust/pullback and rotation pumps 144,146 respectively mounted on a given boring machine chassis. Thevibration threshold values are typically established with the respectivepumps 144, 146 mounted on the boring machine, since the boring machinechassis influences that vibratory characteristics of the thrust/pullbackand rotation pumps 144, 146 during operation. A vibration thresholdtypically represents a level of vibration which is considereddetrimental to a given pump. A baseline set of vibration data may thusbe established for each of the thrust/pullback and rotation pumps 144,146, and, in addition, the boring machine engine and chassis if desired.

If vibration levels as monitored by the vibration sensors 150, 160 orchassis vibration sensors during boring activity exceed a givenvibration threshold, the machine controller 74 may adjust one or both ofthe output of the thrust/pullback and rotation pumps 144, 146 until theapplicable vibration threshold is no longer exceeded. Closed-loopvibration sensing and thrust/pullback and rotation pump outputcompensation may thus be effected by the machine controller 74 to avoidover-stressing and damaging the thrust/pullback and rotation pumps 144,146. A similar control approach may be implemented to compensate forexcessively high levels of mud pump and engine vibration. Various knowntypes of vibration sensors/transducers may be employed, including singleor multiple accelerometers for example.

In accordance with another embodiment, an acoustic profile may beestablished for each of the thrust/pullback and rotation pumps 144, 146.An acoustic profile in this context represents an acousticcharacterization of a given pump or motor when operating normally or,alternatively, when operating abnormally. The acoustic profile for agiven boring machine component is typically developed empirically.

Acoustic sampling of a given pump or motor may be conducted on a routinebasis during boring machine operation. The sampled acoustic data for agiven pump or motor may then be compared to its corresponding acousticprofile. Significant differences between the acoustic sample and profilefor a particular pump or motor may indicate a potential problem with thepump/motor. In an alternative embodiment, the acoustic profile mayrepresent an acoustic characterization of a defective pump or motor. Ifthe sampled acoustic data for a given pump/motor appears to be similarto the defective acoustic profile, the potentially defective pump/motorshould be identified and subsequently evaluated. A number of knownanalog signal processing techniques, digital signal processingtechniques, and/or pattern recognition techniques may be employed todetect suspect pumps, motors or other system components when using anacoustic profiling/sampling procedure of the present invention.

This acoustic profiling and sampling technique may be used forevaluating the operational state of a wide variety of boringmachine/boring tool components. By way of example, a given boring toolmay exhibit a characteristic acoustic profile when operating properly.Use of the boring tool during excavation alters the boring tool in termsof shape, size, mass, moment of inertia, and other physical aspects thatimpact the acoustic characteristics of the boring tool. A worn ordamaged boring tool or component of the tool will thus exhibit anacoustic profile different from a new or undamaged boringtool/component. During a drilling operation, sampling of boring toolacoustics, typically by use of a microphonic or piezoelectric device,may be performed. The sampled acoustic data may then be compared withacoustic profile data developed for the given boring tool. The acousticprofile data may be representative of a boring tool in a nominal stateor a defective state.

In a similar manner, the frequency characteristics of a given componentmay also be used as a basis for determining the state of the givencomponent. For example, the frequency spectrum of a cutting bit duringuse may be obtained and evaluated. Since the frequency response of acutting bit changes during wear, the amount of wear and general state ofthe cutting bit may be determined by comparing sampled frequency spectraof the cutting bit with its normal or abnormal frequency profile.

The machine controller 74 also controls the direction of the boring tool181 during a boring operation in response to control signals receivedfrom the central processor. The machine controller 74 controls boringtool direction using one or a combination of steering techniques. Inaccordance with one steering approach, the orientation 170 of the boringtool 181 is determined by the machine controller 74. The boring tool 181is rotated to a selected position and an actuator internal or externalto the boring tool 181 is activated so as to urge the boring tool 181 inthe desired direction.

By way of example, a fluid may be communicated through the drill string180 and delivered to an internal actuator of the boring tool 181, suchas a movable element mounted in the boring tool 181 transverse orsubstantially non-parallel with respect to the longitudinal axis of thedrill string 180. The machine controller 74 controls the delivery offluid impulses to the movable element in the boring tool 181 to effectthe desired lateral movement. In another embodiment, one or moreexternal actuators, such as plates or pistons for example, may beactuated by the machine controller 74 to apply a force against the sideof the borehole so as to move the boring tool 181 in the desireddirection.

In accordance with the embodiment shown in FIG. 10, enhanced directionalsteering of the boring tool 181 is effected in part by controlling theoff-axis angle, θ, of a steering plate 223. Steering plate 223 may takethe form of a structure often referred to in the industry as a duckbillor an adjustable plate or other member extendable from the body of theboring tool 181. The steering controller 116 may adjust the magnitude ofboring tool steering changes, and thus drill string curvature, beforeand during a change in boring tool direction by dynamically controllingthe movement of the steering plate 223.

For example, moving the steering plate 223 toward an angular orientationof θ₂ relative to the longitudinal axis 221 of the boring tool 181results in decreasing rates of off-axis boring tool displacement and acorresponding decrease in drill string curvature. Moving the steeringplate 223 toward an angular orientation of θ, relative to thelongitudinal axis 221 results in increasing rates of off-axis boringtool displacement and a corresponding increase in drill stringcurvature. The steering plate 223 may be adjusted in terms of off-axisangle, θ, and may further be adjusted in terms of displacement throughangles orthogonal to off-axis angle, θ. For example, movable support 232may be rotated about an axis non-parallel to the longitudinal axis 221of the boring tool 181 separate from or in combination with controlledchanges to the off-axis angle, θ, of a steering plate 223.

In accordance with another embodiment, steering of the boring tool 22may be effected or enhanced by use of one or more fluid jets provided atthe boring tool 181. The boring tool embodiment shown in FIG. 9 includestwo fluid jets 224, 225 which are controllable in terms of jet nozzlespray direction, nozzle orifice size, fluid delivery pressure, and fluidflow rate/volume. Fluid jet 224, for example, may be controlled bysteering controller 116 to deliver a pressurized jet of fluid in adesired direction, such as direction D₁₋₁, D₁₋₂ or D₁₋₃, for example.Fluid jet 254, separate from or in combination with fluid jet 224, mayalso be controlled to deliver a pressurized jet of fluid in a desireddirection, such as direction D₂₋₁, D₂₋₂ or D₂₋₃, for example. Themachine controller 74 may also adjust the size of the orifice whichassists in moderating the pressure and flow rate/volume of fluiddelivered through the jet nozzles 224, 225.

The machine controller 74 may also dynamically adjust the physicalconfiguration of the boring tool 181 to alter boring tool steeringand/or productivity characteristics. The portion 240 of a boring toolhousing depicted in FIG. 11 includes two cutting bits 244, 254 which maybe situated at a desired location on the boring tool 181, it beingunderstood that more or less than two cutting bits may be employed. Eachof the cutting bits 244, 254 may be adjusted in terms of displacementheight and/or angle relative to the boring tool housing surface 240. Thecutting bits 244, 254 may also be rotated to expose particular surfacesof the cutting bit (e.g., unworn portion) to the soil/rock subjected toexcavation. A bit actuator 248, 258 responds to hydraulic, mechanical,or electrical control signals to dynamically adjust the position and/ororientation of the cutting bits 244, 254 during a boring operation. Themachine controller 74 may control the movement of the cutting bits 244,254 for purposes of enhancing boring tool productivity, steering orimproving the wearout characteristics of the cutting bits 244, 254.

The machine controller 74 may also obtain cutting bit wear data throughuse of a sensing apparatus provided in the boring tool 181. In theembodiment shown in FIG. 12, a cutting bit 262 comprises a number ofintegral sensors 264 situated at varying depths within the cutting bit262. As the cutting bit 262 wears during usage, an uppermost sensor264′″ becomes exposed. A detector 266 detects the exposed condition ofsensor 264′″ and transmits a corresponding cutting bit status signal tothe machine controller 74. As the cutting bit 262 is subjected tofurther wear, intermediate wear sensor 264″ becomes exposed, causingdetector 266 to communicate a corresponding cutting bit status signal tothe machine controller 74. When the lowermost sensor 264′ becomesexposed due to continued wearing of cutting bit 262, detector 266communicates a corresponding cutting bit status signal to the machinecontroller 74, at which point a warning signal indicating detection ofan excessively worn cutting bit 262 is transmitted by the machinecontroller 74 to the central processor 72 and ultimately to theoperator. The wear sensors 264 may constitute respective insulatedconductors in which a voltage across or current passing therethroughchanges as the insulation is worn through. Such a change in voltageand/or current is detected by the detector 266.

Each of the cutting bits 262 provided on the boring tool 181 may beprovided with a single wear sensor or multiple wear sensors 264. Thedetector 266 associated with each of the cutting bits 262 may transmit aunique cutting bit status signal that identifies the particular cuttingbit and its associated wear data. In the case of multiple wear sensors264 provided for individual cutting bits 262, the detector 266associated with each of the cutting bits 262 transmits a unique cuttingbit status signal that identifies the affected cutting bit and wearsensor associated with the wear data. This data may be used by themachine controller 74 to modify the configuration, orientation, and/orproductivity of the boring tool 181 during a given boring operation.

Referring now to FIG. 13, there is depicted a block diagram of a controlsystem for controlling the delivery of a fluid, such as water, mud,foam, air or other fluid composition, to a boring tool 181 during aboring operation, such fluids being referred to herein generally as mudfor purposes of clarity. In accordance with this embodiment, the machinecontroller 74 controls the delivery, viscosity, and composition of mudsupplied through the drill string 180 and to boring tool 181. A mud tank201 defines a reservoir of mud which is supplied to the drill string 180under pressure provided by a mud pump 200. The mud pump 200 receivescontrol signals from the machine controller 74 which, in response tosame, modifies the pressure and/or flow rate of mud delivered throughthe drill string 180.

Automatic closed-loop control of the mud pump 200 is provided by themachine controller 74 in cooperation with various sensors that sense theproductivity of the boring tool and boring machine as discussed above.Mud is pumped through the drill pipe 180 and boring tool 181 orbackreamer (not shown) so as to flow into the borehole during respectivedrilling and reaming operations. The fluid flows out from the boringtool 181, up through the borehole, and emerges at the ground surface.The flow of fluid washes cuttings and other debris away from the boringtool 181 or reamer, thereby permitting the boring tool 181 or reamer tooperate unimpeded by such debris. The rate at which fluid is pumped intothe borehole by the mud pump 200 is typically dependent on a number offactors, including the drilling rate of the boring machine and thediameter of the boring tool 181 or backreamer. If the boring tool 181 orreamer is displaced at a relatively high rate through the ground, forexample, the machine controller 74, typically in response to a controlsignal received from the central processor 72, transmits a signal to themud pump 200 to increase the volume of fluid dispensed by the mud pump200.

It will be understood that the various computations, functions, andcontrol aspects described herein may be performed by the machinecontroller 74, the central processor 72, or a combination of the twocontrollers 74, 72. It will be further understood that the operationsperformed by the machine controller 74 as described herein may beperformed entirely by the central processor 72 alone or in cooperationwith one or more other local or remote processors.

The machine controller 74 and/or central processor 72 may optimize theprocess of dispensing mud into the borehole by monitoring the rate ofboring tool or backreamer displacement and computing the materialremoval rate as a result of such displacement. For example, the rate ofmaterial removal from the borehole, measured in volume per unit time,can be estimated by multiplying the displacement rate of the boring tool181 by the cross-sectional area of the borehole produced by the boringtool 181 as it advances through the ground. The machine controller 74 orcentral processor 72 calculates the estimated rate of material removedfrom the borehole and the estimated flow rate of fluid to be dispensedthrough the mud pump 200 in order to accommodate the calculated materialremoval rate. The central processor 72 may also multiply the volumeobtained from the above calculations by the mud volume-to-hole volumeratio selected by the operator for the soil/rock in the current soilstrata. This can also be performed automatically based upon thesoil/rock data received from the GPR and/or other sensors. For example,a course sandy soil may require a mud-to-hole volume ratio of 5, inwhich case the amount of mud pumped into the hole is 5 times the holevolume.

A fluid dispensing sensor (not shown) detects the actual flow rate offluid through the mud pump 200 and transmits the actual flow rateinformation to the machine controller 74 or central processor 72. Themachine controller 74 or central processor 72 then compares thecalculated liquid flow rate with the actual liquid flow rate. Inresponse to a difference therebetween, the machine controller 74 orcentral processor 72 modifies the control signal transmitted to the mudpump 200 to equilibrate the actual and calculated flow rates to withinan acceptable tolerance range.

The machine controller 74 or central processor 72 may also optimize theprocess of dispensing fluid into the borehole for a back reamingoperation. The rate of material removal in the back reaming operation,measured in volume per unit time, can be estimated by multiplying thedisplacement rate of the boring tool 181 by the cross-sectional area ofmaterial being removed by the reamer. The cross-sectional area ofmaterial being removed may be estimated by subtracting thecross-sectional area of the reamed hole produced by the reamer advancingthrough the ground from the cross-sectional area of the boreholeproduced in the prior drilling operation by the boring tool 181.

In a procedure similar to that discussed in connection with the drillingoperation, the machine controller 74 or central processor 72 calculatesthe estimated rate of material removed from the reamed hole and theestimated flow rate of liquid to be dispensed through the liquiddispensing pump 58 in order to accommodate the calculated materialremoval rate.

The fluid dispensing sensor detects the actual flow rate of liquidthrough the mud pump 200 and transmits the actual flow rate informationto the machine controller 74 or central processor 72, which thencompares the calculated liquid flow rate with the actual liquid flowrate. In response to a difference therebetween, the machine controller74 or central processor 72 modifies the control signal transmitted tothe mud pump 200 to equilibrate the actual and calculated flow rates towithin an acceptable tolerance range.

In accordance with an alternative embodiment, the machine controller 74or central processor 72 may be programmed to detect simultaneousconditions of high thrust/pullback pump pressure and low rotation pumppressure, detected by sensors 152 and 162 respectively shown in FIG. 8.Under these conditions, there is an increased probability that theboring tool 181 is close to seizing in the borehole. This anomalouscondition is detected when the pressure of the thrust/pullback pump 144detected by sensor 152 exceeds a first predetermined level, and when thepressure of the rotation pump 146 detected by sensor 162 falls below asecond predetermined level. Upon detecting these pressure conditionssimultaneously, the machine controller 74 or central processor 72 mayincrease the mud flow rate by transmitting an appropriate signal to themud pump 200 and thus prevent the boring tool 181 from seizing.Alternatively, the machine controller 74 or central processor 72 may beprogrammed to reduce the displacement rate of the boring tool 181 whenthe conditions of high thrust/pullback pump pressure and low rotationpump pressure exist simultaneously, as determined in the mannerdescribed above.

As is further shown in FIG. 13, the machine controller 74 may alsocontrol the viscosity of fluid delivered to the boring tool 181. Themachine controller 74 communicates control signals to a mud viscositycontrol 202 to modify mud viscosity. Mud viscosity control 202 regulatesthe flow of a thinning fluid, such as water, received from a fluidsource 203. Fluid source 203 may represent a water supply, such as amunicipal water supply, or a tank or other stationary or mobile fluidsupply. The viscosity of the mud contained in the mud tank 201 may bereduced by increasing the relative volume of thinning fluid containedinto the mud tank 201. In this case, the machine controller 74 transmitsa control signal to the mud viscosity control 202 to increase tothinning fluid volume delivered to the mud tank 201 until the desiredviscosity is achieved.

The viscosity of the mud contained in the mud tank 201 may be increasedby increasing the relative volume of solids contained into the mud tank201. The machine controller 74 controls an additives pump/injector 206which injects a solid or slurry additive into the mud tank 201. In oneembodiment, the contents of the mud tank 201 are circulated through themud viscosity control 202 and additives pump/injector 206 such thatthinning fluid and/or solid additives may be selectively mixed into thecirculating mud mixture during the mud modification process to achievethe desired mud viscosity and composition.

In accordance with another embodiment, and with continued reference toFIG. 13, the composition of the mud contained in the mud tank 201 anddelivered to the boring tool 181 may be altered by selectively mixingone or more additives to the mud tank contents. It is understood thatsoil/rock characteristics can vary dramatically among excavation sitesand among locations within a single excavation site. It may be desirableto tailor the composition of mud delivered to the boring tool 181 to thesoil/rock conditions at a particular boring site or at particularlocations within the boring site. A number of different mud additives,such as powders, may be selectively injected into the mud tank 201 froma corresponding number of mud additive units 208, 210, 212.

Upon determining the soil or rock characteristics either manually orautomatically in a manner discussed above (e.g., using GPR imaging orother geophysical sensing techniques), the machine controller 74controls the additives pump/injector 206 to select and deliver anappropriate mud additive from one or more of the mud additive units 208,210, 212. Since the soil/rock characteristics may change during a boringoperation, the mud additives controller may adaptively deliverappropriate mud additives to the mud tank 201 or an inlet downstream ofthe mud tank 201 to enhance the boring operation.

The presence or lack of mud exiting a borehole may also be used as acontrol system input which may be evaluated by the machine controller74. A return mud detector 205 may be situated at the entrance pitlocation and used to determine the volume and composition of mud/cuttingreturn coming out of the borehole. A spillover vessel may be placed nearthe entrance pit and preferably situated in a dug out section such thatsome of the mud exiting the borehole will spill into the spillovervessel. The return mud detector 205 may be used to detect the presenceor absence of mud in the spillover vessel during a boring operation. Ifmud is not detected in the spillover vessel, the machine controller 74increases the volume of mud introduced into the borehole.

The volume of mud may also be estimated using a flow meter and thecross-sectional dimensions of the borehole. If the volume of return mudis less than desired, the machine controller 74 may increase the volumeof mud introduced into the borehole until the desired return mud volumeis achieved. The cuttings coming out the borehole may also be analyzed,the results of which may be used as an input to the boring controlsystem. An optical sensor, for example, may be situated at the boreholeentrance pit location for purposes of analyzing the size of thecuttings. The size of the cuttings exiting the borehole may be used as afactor for determining whether the boring tool is operating as intendedin a given soil/rock type. Other characteristics of the cutting returnsmay be analyzed.

Referring now to FIG. 14, there is illustrated a block diagram showingthe direction of sense and control signals through a close-loop,real-time boring control system according to an embodiment of thepresent invention. According to this embodiment, the central processor72 receives a number of inputs from various sensors provided within thedown-hole sensor unit 189 of a boring tool 181 and various sensorsprovided on the boring machine pumps, engines, and motors. The centralprocessor 72 also receives data from a bore plan software and databasefacility 78, a geographic reference unit 76, geophysical sensors 112,and a user interface 184. Using these data and signal inputs, thecentral processor 72 optimizes boring machine/boring tool productivitywhile excavating along a pre-planned bore path and, if necessary,computes an on-the-fly alternative bore plan so as to minimize drillstring/boring tool/boring machine stress and to avoid contact withburied hazards, obstacles and undesirable geology.

By way of example, the central processor 72 may modify a givenpre-planned bore plan upon detecting an appreciable change in boringtool steering behavior. A steerability factor may be assigned to a givenpre-planned bore path. The steerability factor is an indication of howquickly the boring tool can change direction (i.e., steer) in a givengeology, and may be expressed in terms of rate of change of boring toolpitch or yaw as the boring tool moves longitudinally. If the soil/rocksteerability factor indicates that the actual drill string curvaturewill be flatter than the planned curvature, which generally results inlower drill string stress, the central processor 72 may modify thepre-planned bore path accordingly so that critical underground targetscan be drilled through.

As is shown in FIG. 14, the central processor 72 receives input signalsfrom the various sensors of the boring tool down-hole sensor unit 189,which may include one or more geophysical sensors 198, accelerometers197, magnetometers 196, and one or more environmental sensors 195. Thesensor input signals are preferable acquired by the central processor 72in real-time. The central processor 72 also receives input signals fromthe thrust/pullback pump pressure and vibration sensors 152, 150,rotation pump pressure and vibration sensors 162, 160, mud pump pressureand vibration sensors 165, 163, and other vibration sensors that may bemounted to the boring machine structure/chassis. An input signalproduced by an engine sensor 167 is also received by the centralprocessor 72. User input commands are also received by the centralprocessor 72 via a user interface 184. The central processor 72 alsoreceives input data from one or more automatic rod loader sensors 168.

In response to these input signals, operator input signals, and inaccordance with a selected bore plan, the central processor 72 controlsboring machine operations to produce the desired borehole along theintended bore path as efficiently and productively as possible. Incontrolling the thrust/pullback pump 144, for example, the centralprocessor 72 produces a primary control signal, S_(A), which isrepresentative of a requested level of thrust/pullback pump output(i.e., pressure). The primary control signal, S_(A), may be modified bya compensation signal, S_(B), in response to the various boring tool andboring machine sensor input signals received by the central processor72.

The process of modifying the primary control signal, S_(A), by use ofthe compensation signal, S_(B), is depicted by a signal summingoperation performed by a signal summer S1. At the output of the signalsummer S1, a thrust/pullback pump control signal, CS₁, is produced. Thethrust/pullback pump control signal, CS₁, is applied to thethrust/pullback pump 144 to effect a change in thrust/pullback pumpoutput. It is noted that the compensation signal, S_(B), may have anappreciable effect or no effect (i.e., zero value) on the primarycontrol signal, S_(A), depending on the sensor input and bore plan databeing evaluated by the central processor 72 at a given moment.

The central processor 72 also produces a primary control signal, S_(C),which is representative of a requested level of rotation pump output,which may be modified by a compensation signal, S_(D), in response tothe various boring tool and boring machine sensor input signals receivedby the central processor 72. A rotation pump control signal, CS₂, isproduced at the output of the signal summer S2 and is applied to therotation pump 146 to effect a change in rotation pump output.

In a similar manner, the central processor 72 produces a primary controlsignal, S_(E), which is representative of a requested level of mud pumpoutput, which may be modified by a compensation signal, S_(F), inresponse to the various boring tool and boring machine sensor inputsignals received by the central processor 72. A mud pump control signal,CS₃, is produced at the output of the signal summer S3 and is applied tothe mud pump 200 to effect a change in mud pump output.

The central processor 72 may also produce a primary control signal,S_(G), which is representative of a requested level of boring machineengine output, which may be modified by a compensation signal, S_(H), inresponse to the various boring tool and boring machine sensor inputsignals received by the central processor 72. An engine control signal,CS₄, is produced at the output of the signal summer S4 and is applied tothe engine 169 to effect a change in engine performance.

In accordance with another embodiment of the present invention, and withreference to FIGS. 15-17, a remote control unit provides an operatorwith the ability to control all or a sub-set of boring system functionsand activities. According to this embodiment, an operator initiatesboring machine and boring tool commands using a portable control unit,an embodiment of which is depicted in FIG. 16. Referring to FIG. 15A,there is illustrated a diagram which depicts the flow of various signalsbetween a remote unit 304 and a horizontal directional drilling (HDD)machine 302. According to this system configuration, which represents aless complex implementation, the boring tool 181 is of a conventionaldesign and includes a transmitter 308 for transmitting a sonde signal.The transmitter 308 may alternatively be configured as a transceiver forreceiving signals from the remote unit 304 in addition to transmittingsonde signals.

In one embodiment, the remote unit 304 has standard features andfunctions equivalent to those provided by conventional locators. Theremote unit 304 also includes a transceiver 306 and various controlsthat cooperate with the transceiver 306 for sending boring and steeringcommands 312 to the HDD 302. The remote unit 304 may include all or someof the controls and displays depicted in FIG. 16, which will bedescribed in greater detail hereinbelow. The HDD 302 includes atransceiver (not shown) for receiving the boring/steering commands 312from the remote unit 304 and for sending HDD status information 310 tothe remote unit 304. The HDD status information is typically presentedon a display provided on the remote unit 304. The HDD 302 incorporates acentral processor and associated interfaces to implement boring andsteering changes in response to the control signals received from theremote unit 304.

FIG. 15B illustrates a more complex system configuration which providesan operator the ability to communicate with down-hole electronicsprovided within or proximate the boring tool 181. According to onesystem configuration, the remote unit 324 has standard features andfunctionality equivalent to those provided by conventional locators. Inaddition, the remote unit 324 includes a transceiver 326 which transmitsand receives electromagnetic (EM) signals. The transceiver 326 of theremote unit 324 transmits boring and steering commands 333 to thedown-hole electronics which are received by the transceiver 328 of theboring tool 181.

The down-hole electronics process the boring and steering commands and,in response, communicate the commands to the HDD 322 to implement boringand steering changes. In one embodiment, the boring tool electronicsrelay the boring/steering command received from the remote unit 324essentially unchanged to the HDD 322. In another embodiment, thedown-hole electronics process the boring/steering command and, inresponse, produce HDD control signals which effect the necessary changesto boring machine/boring tool operation.

The boring tool commands may be communicated from the boring tool 181 tothe HDD 322 via a wire-line 331 or wireless communication link 330, 332.The wireless communication link 330, 332 may be established via theremote unit 324 or other transceiving device. The HDD 322 communicatesHDD status information to the remote unit 324 via a wire-linecommunication link 336, 338 or a wire-less communication link 334. It isunderstood that a communication link established via the drill stringmay incorporate a physical wire-line, but may also be implemented usingother transmission means, such as those described herein and those knownin the art.

A variation of the embodiment depicted in FIG. 15B provides for theabove-described functionality and, in addition, provides the capabilityto dynamically modify the boring tool steering commands received fromthe remote unit 324. The data acquired and produced by the down-holesensor unit of the boring tool 181 may be processed by the down-holeelectronics and used to modify the boring/steering commands receivedfrom the remote unit 324. The down-hole electronics, for example, maygenerate or alter mud pump and thrust/pullback pump commands, inaddition to rotation pump commands, in response to boring/steeringcommands 333 received from the remote unit 324 and other data obtainedfrom various navigation and geophysical sensors. The down-holeelectronics may also produce local control signals that modify thevarious steering mechanisms of the boring tool, such as fluid jetdirection and orifice size, steering plate/duckbill angle of attack,articulated head angle and/or direction, bit height and angle, and thelike.

By way of further example, an in-tool or above-ground GPR unit maydetect the presence of an obstruction several feet ahead of the boringtool. The GPR data representative of the detected obstruction istypically presented to the operator on a display of the remote unit 324.The operator may issue steering commands to the boring tool 181 in orderto avoid the obstruction. In response to the steering commands, thedown-hole electronics may further modify the operator issued steeringcommands based on various data to ensure that the obstruction isavoided. For example, the operator may issue a steering command that maycause avoidance of an obstruction, but not within a desired safetymargin (e.g., 2 feet). The down-hole electronics, in this case, maymodify the operator issued steering commands so that the obstruction isavoided in a manner that satisfies the minimum safety clearancerequirement associated with the particular obstruction.

Turning now to FIG. 16, there is depicted an embodiment of a remote unit350 that may be used by an operator to control all or a sub-set ofboring machine functions that affect the productivity and steering ofthe boring tool during a boring operation. According to this embodiment,the remote unit 350 includes a steering direction control 352 with whichthe operator controls boring tool orientation and rate of boring toolrotation. The steering direction control 352 may include a joystick 356which is moved by the operator to direct the boring tool in a desiredheading. The steering direction control 352 includes a clock facedisplay 354 with appropriate hour indicators. The operator moves thesteering direction joystick 356 to a desired clock position, such as a3:00 position, typically by rotating the joystick about its axis to thedesired position.

The joystick may also be moved in a forward and reverse direction at agiven clock position to vary the boring tool rotation rate as desired.In response to a selected joystick position and displacement, the boringmachine provides the necessary rotation and thrust to modify the presentboring tool location and orientation so as to move the boring tool tothe requested position/heading at the requested degree of steepness. Itis understood that other steering related processes may also be adjustedusing the remote unit 350 to achieve a desired boring tool heading, suchas mud flow changes, fluid jet and steering surface changes, and thelike.

The remote unit 350 further includes a drilling/pullback rate control358 for controlling the amount of force applied to the drill string inthe forward and reverse directions, respectively. Alternatively,drilling/pullback rate control 358 controls the thrust speed of thedrill string in the forward and reverse directions, respectively. Thedrilling/pullback rate control 358 includes a lever control 360 that ismovable in a positive and negative direction to effect forward andreverse displacement changes at variable thrust force/speed levels.Moving the lever control 360 in the positive (+) direction results inforward displacement of the boring tool at progressively increasingthrust force/speed levels. Moving the lever control 360 in the negative(−) direction results in reverse displacement (i.e., pullback) of theboring tool at progressively increasing thrust force/speed levels.

The drilling/pullback rate control 358, as well as the steeringdirection control 352, may be operable in one of several differentmodes, such as a normal drilling mode and a creep mode. A mode selectswitch 377 may be used to select a desired operating mode. A creep modeof operation allows the remote operator to slowly and safely displaceand rotate the boring tool at substantially reduced rates. Such reducedrates of rotation and displacement may be required when steering theboring tool around an underground obstruction or when operating near ordirectly with the boring tool, such as at an exit location. It isunderstood that the control features and functionality described withreference to the remote unit 350 may be incorporated at the boringmachine for use in locally controlling a boring operation.

FIG. 17 illustrates two boring tool steering scenarios that may beachieved using the remote unit 350 shown in FIG. 16. The boring tool ismoved along an underground path to a target location A at which pointthe boring tool is steered toward the surface at two distinctlydifferent angles of assent. Bore path 382 represents a steeper andshorter route to the earth's surface relative to bore path 384, which isshown as a more gradual and longer route. Starting at location A, thesteeper bore path 382 may be achieved by displacing the steeringdirection joystick 356 in a direction toward the periphery of thecircular clock display 354. Higher levels of thrust displacement orother steering actuation are achieved in response to greaterdisplacement of the joystick 356 outwardly from a neutral (i.e.,non-displaced) position toward the periphery of the circular clockdisplay 354. The more gradual bore path 384 may be achieved by leavingthe joystick 356 near its neutral or non-displaced position. Lowerlevels of thrust displacement or other steering actuation are achievedin response to minimal or zero displacement of the joystick 356 relativeto its neutral position.

In accordance with another embodiment, steering of the boring tool maybe accomplished in one of several steering modes, including a hardsteering mode and a soft steering mode. Both of these steering modes areassumed to employ the rotation and thrust/pullback pump controlcapabilities previously described above with reference to co-owned U.S.Pat. No. 5,746,278. According to a hard steering mode, positioning ofthe joystick 356 allows the operator to modulate the thrust pumppressure during the cut. In particular, the boring tool is thrustforward until the thrust/pullback pump pressure limit, as dictated bythe preset joystick 356 position, is met, at which time the boring toolis rotated in the prescribed manner as indicated by the cuttingduration. The cutting duration refers to the number of clock-facesegments the boring tool will sweep through. The cutting duration is setby use of a cutting duration control 375 provided on the remote unit350. This process is repeated until the selected boring tool heading isachieved.

In accordance with a soft steering mode, positioning of the joystick 356allows the operator to modulate the distance of boring tool travelbefore it is rotated by the prescribed amount as indicated by thecutting duration. In particular, the boring tool is thrust forward for apre-established travel distance, and, simultaneously, the boring tool isrotated through the cutting duration. This process is repeated until thedesired boring tool heading is achieved.

In accordance with another steering mode of the present invention whichemploys a rockfire cutting action, the boring tool 24 is thrust forwarduntil the boring tool begins its cutting action. Forward thrusting ofthe boring tool continues until a preset pressure for the soilconditions is met. The boring tool is then rotated clockwise through thecutting duration while maintaining the preset pressure. In the contextof a rockfire cutting technique, the term pressure refers to acombination of torque and thrust on the boring tool. Clockwise rotationof the boring tool is terminated at the end of the cutting duration andthe boring tool is pulled back until the pressure at the boring tool iszero. The boring tool is then rotated clockwise to the beginning of theduration. This process is repeated until the desired boring tool headingis achieved.

In accordance with another embodiment of a steering mode which employs arockfire cutting action, the boring tool 24 is thrust forward until theboring tool begins its cutting action. Forward thrusting of the boringtool continues until a preset pressure for the soil conditions is met.The boring tool is then rotated clockwise through the cutting durationwhile maintaining the preset pressure. Clockwise rotation of the boringtool is terminated at the end of the cutting duration. The boring toolis then rotated counterclockwise while maintaining a torque that isabout 60% less than the makeup torque required for the drill rod in use.If the torque is too large, counterclockwise rotation of the boring toolis reduced or terminated and the boring tool is pulled back until about60% of the makeup torque is reached. Counterclockwise rotation of theboring tool continues until the beginning of the cutting duration. Theprocess is repeated until the desired boring tool heading is achieved.

In accordance with yet another advanced steering capability, thetorsional forces that act on the drill string during a drillingoperation are accounted for when steering the boring tool. It iswell-understood in the art of drilling that residual rotation of theboring tool occurs after ceasing rotation of the drill string at thedrilling machine due to a torsional spring affect commonly referred toas torsional wind-up or pipe wrap. The degree to which residual boringtool rotation occurs due to torsional wind-up is determined by a numberof factors, including the length and diameter of the drill string, thetorque applied to the drill string by the boring machine, and dragforces acting on the drill string by the particular type of soil/rocksurrounding the drill string.

When steering a boring tool to follow a desired heading, a commontechnique used to steer the boring tool involves rotating the tool to aselected orientation needed to effect the steering change, ceasingrotation of the tool at the selected orientation, and then thrusting theboring tool forward. This process is repeated to achieve the desiredboring tool heading. Given the effects of torsional wind-up, however, itcan be appreciated that stopping the rotating boring tool at a desiredorientation is difficult. Conventional steering approaches require theuse of a portable locator to confirm that the boring tool is properlyoriented prior to applying thrust forces to the boring tool.- The remoteoperator must cooperate with the boring machine operator to ensure thatthe boring tool is neither under-rotated or over-rotated prior to theapplication of thrust forces. The process of manually assessing andconfirming the orientation of the boring tool to effect heading changesis time consuming and costly in terms of operator resources.

An adaptive steering approach according to the present inventioncharacterizes the torsional wind-up behavior of a given drilling stringand updates this characterization as the drill string is adjusted interms of length and curvature. Using the acquired wind-upcharacterization data, the boring tool may be rotated to the desiredorientation without the need for operator intervention. For example,torsional wind-up at a particular boring tool location may account forresidual rotation of 80 degrees. Earlier acquired data may indicate thatthe rate of wind-up has been increasing substantially linearly at a rateof 1 degree per 20 feet of additional drill string length. Based onthese data, the residual rotation of the boring tool at the next turninglocation may be estimated using an appropriate extrapolation algorithm.It is understood that the degree of wind-up may increase in a non-linearmanner as function of additional drill string length, and that anappropriate non-linear extrapolation algorithm should be applied to thedata in this case.

In this illustrative example, it is assumed that the estimated residualrotation that will occur at the next turning location is computed to be84 degrees. The estimated residual rotation may be accounted for at thedrilling machine, such that the boring machine ceases drill stringrotation to allow the boring tool to rotate an additional 84 degrees tothe intended orientation needed to effect the steering change. If, forexample, over-rotation occurs at the next turning location due tounexpected changes in soil/rock composition, the historical and currenttorsional wind-up characterization data may be used to cause to thedrilling machine to rotate the boring tool to the proper orientation inview of the changed soil/rock characteristics (e.g., actual torsionalwind-up resulted in 88 degrees of residual boring tool rotation, insteadof the estimated 86 degrees of residual rotation due to unexpectedincrease in soil/rock drag forces).

It will be appreciated that the torsional wind-up behavior of a givendrill string may be characterized in other ways, such as by use ofvelocity and/or acceleration profiles. By way of example, anacceleration or velocity profile may be developed that characterizes thechange of drill string rotation during torsional wind-up. In particular,the acceleration or velocity of the drill string between the time thedrilling machine ceases to rotate the drill string and the time whenresidual boring tool rotation ceases may be characterized to developwind-up acceleration/velocity profile data. These data may be used toestimate the torsional wind-up behavior of the drill string at a giventurning location so that the boring tool rotates to the desiredorientation after residual rotation of the boring tool ceases.

An adaptive approach may also be employed when initiating rotation ofthe drill string, and is of particular use when reinitiating rotation ofa relatively long drill string. Characterizing the initial drill stringrotation behavior allows for a high degree of control when making small,slow changes to boring tool rotation. Such a control capability isdesirable when operators are working on or closely to the boring tool. Arotation sensor may be used to determine how far the gearbox of therotation unit rotates before the boring tool rotates. This differentialin gearbox and boring tool rotation results from torsional wind-upeffects as discussed above. This differential may be monitored andcompensated for when initiating drill string rotation to rotate theboring tool to a desired orientation.

With continued reference to FIG. 16, a warning indicator 374 may beprovided to alert the operator as to an impending collision situation.The warning indicator 374 may be an illuminatable indicator, a speakerthat broadcasts an audible alarm or a combination of visual and audibleindicators. A kill switch 376 is provided to allow the operator toterminate all drilling related activities when appropriate. A modeselect switch 377 provides for the selection of one of a number ofdifferent operating modes, such as a normal drilling mode, a creep mode,a backreaming mode, and transport mode, for example.

Several displays are provided on the remote unit 350. Various dataconcerning boring machine status and activity are presented to theoperator on a boring machine status display 362. Various data concerningthe status of the boring tool are presented to the operator via a boringtool status display 366. Boring tool steerability factor data may alsobe displayed within an appropriate display window 364. Planned andactual bore path data may be presented on appropriate displays 370, 372.It is understood that the type of data displayable on the remote unit350 may vary from that depicted in FIG. 16. For example, GPR imagingdata or other geophysical sensor data may be graphically presented on anappropriate display, such as imaging data associated with man-made andgeologic structures. Also, it is appreciated that the various displaysdepicted in FIG. 16 may constitute physically distinct display devicesor individual windows of a single display.

It will, of course, be understood that various modifications andadditions can be made to the preferred embodiments discussed hereinabovewithout departing from the scope of the present invention. Accordingly,the scope of the present invention should not be limited by theparticular embodiments described above, but should be defined only bythe claims set forth below and equivalents thereof.

1. A method, comprising: establishing a bore plan representative of anintended bore; receiving product information concerning a product to beinstalled in the intended bore; drilling a pilot bore in accordance withthe bore plan; and adjusting drilling of the pilot bore in response tothe product information to ensure that the pilot bore accommodates theproduct.
 2. The method of claim 1, wherein the product informationcomprises product diameter.
 3. The method of claim 1, wherein theproduct information comprises allowable bend radius of the product. 4.The method of claim 1, wherein the product information comprisesquantity of the product to be installed in the intended bore.
 5. Themethod of claim 1, wherein the product information comprises safetyclearance between the product to be installed and underground utilitiesor obstacles.
 6. The method of claim 1, wherein the product informationcomprises maximum allowable depth of the product to be installed.
 7. Themethod of claim 1, further comprising receiving ground cover informationconcerning ground cover above the product to be installed in theintended bore, wherein drilling of the pilot bore is adjusted inresponse to the ground cover information.
 8. The method of claim 1,wherein adjusting pilot bore drilling comprises modifying the bore planand determining if pilot bore adjustment is consistent with constraintsof the bore plan.
 9. A method, comprising: establishing a bore planrepresentative of an intended bore; receiving product informationconcerning a product to be installed in the intended bore; estimatingbackreamer deviation from a pilot bore along the intended bore inresponse to the product information; and adjusting drilling of the pilotbore in accordance with the estimated backreamer deviation.
 10. Themethod of claim 9, wherein the product information comprises productdiameter.
 11. The method of claim 9, wherein the product informationcomprises allowable bend radius of the product.
 12. The method of claim9, wherein the product information comprises quantity of the product tobe installed in the intended bore.
 13. The method of claim 9, whereinthe product information comprises safety clearance between the productto be installed and underground utilities or obstacles.
 14. The methodof claim 9, wherein the product information comprises maximum allowabledepth of the product to be installed.
 15. The method of claim 9, furthercomprising receiving ground cover information concerning ground coverabove the product to be installed in the intended bore, wherein drillingof the pilot bore is adjusted in response to the ground coverinformation.
 16. A system, comprising: a cutting tool coupled to a drillstring; a driving apparatus coupled to the drill string; memoryconfigured to store a bore plan representative of an intended bore andproduct information concerning a product to be installed in the intendedbore; and a controller coupled to the driving apparatus and the memory,the controller configured to control the driving apparatus whiledrilling a pilot bore in accordance with the bore plan and to adjustdrilling of the pilot bore in response to the product information toensure that the pilot bore accommodates the product.
 17. The system ofclaim 16, wherein the controller is configured to adjust pilot boredrilling in accordance with an estimated backreamer deviation from thepilot bore along the intended bore in response to the productinformation.
 18. The system of claim 16, further comprising a boreplanning system configured to generate the bore plan.
 19. The system ofclaim 16, wherein the product information comprises product diameter.20. The system of claim 16, wherein the product information comprisesallowable bend radius of the product.